Add MRT example

examples/rhi/mrt/buildshaders.sh

+qsb --glsl "100 es,120" --hlsl 50 --msl 12 mrt.vert -o mrt.vert.qsb
+qsb --glsl "100 es,120" --hlsl 50 --msl 12 mrt.frag -o mrt.frag.qsb

examples/rhi/mrt/mrt.cpp

+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "../shared/examplefw.h"
+
+static float quadVertexData[] =
+{ // Y up, CCW
+  -0.5f,   0.5f,   0.0f, 0.0f,
+  -0.5f,  -0.5f,   0.0f, 1.0f,
+  0.5f,   -0.5f,   1.0f, 1.0f,
+  0.5f,   0.5f,    1.0f, 0.0f
+};
+
+static quint16 quadIndexData[] =
+{
+    0, 1, 2, 0, 2, 3
+};
+
+static float triangleData[] =
+{ // Y up, CCW
+     0.0f,   0.5f,   1.0f, 0.0f, 0.0f,
+    -0.5f,  -0.5f,   0.0f, 1.0f, 0.0f,
+     0.5f,  -0.5f,   0.0f, 0.0f, 1.0f,
+};
+
+struct {
+    QVector<QRhiResource *> releasePool;
+    QRhiBuffer *vbuf = nullptr;
+    QRhiBuffer *ibuf = nullptr;
+    QRhiBuffer *ubuf = nullptr;
+    QRhiTextureRenderTarget *rt = nullptr;
+    QRhiRenderPassDescriptor *rtRp = nullptr;
+    QRhiTexture *tex = nullptr;
+    QRhiSampler *sampler = nullptr;
+    QRhiShaderResourceBindings *srb = nullptr;
+    QRhiGraphicsPipeline *ps = nullptr;
+    QRhiResourceUpdateBatch *initialUpdates = nullptr;
+    QMatrix4x4 winProj;
+
+    QRhiBuffer *triUbuf = nullptr;
+    QRhiShaderResourceBindings *triSrb = nullptr;
+    QRhiGraphicsPipeline *triPs = nullptr;
+    float triRot = 0;
+    QMatrix4x4 triBaseMvp;
+} d;
+
+void Window::customInit()
+{
+    qDebug("Max color attachments: %d", m_r->resourceLimit(QRhi::MaxColorAttachments));
+    if (m_r->resourceLimit(QRhi::MaxColorAttachments) < 4)
+        qWarning("MRT is not supported");
+
+    d.vbuf = m_r->newBuffer(QRhiBuffer::Immutable, QRhiBuffer::VertexBuffer, sizeof(quadVertexData) + sizeof(triangleData));
+    d.vbuf->build();
+    d.releasePool << d.vbuf;
+
+    d.ibuf = m_r->newBuffer(QRhiBuffer::Immutable, QRhiBuffer::IndexBuffer, sizeof(quadIndexData));
+    d.ibuf->build();
+    d.releasePool << d.ibuf;
+
+    d.ubuf = m_r->newBuffer(QRhiBuffer::Dynamic, QRhiBuffer::UniformBuffer, 68);
+    d.ubuf->build();
+    d.releasePool << d.ubuf;
+
+    d.tex = m_r->newTexture(QRhiTexture::RGBA8, QSize(512, 512), 1, QRhiTexture::RenderTarget);
+    d.releasePool << d.tex;
+    d.tex->build();
+
+    d.rt = m_r->newTextureRenderTarget({ d.tex });
+    d.releasePool << d.rt;
+    d.rtRp = d.rt->newCompatibleRenderPassDescriptor();
+    d.releasePool << d.rtRp;
+    d.rt->setRenderPassDescriptor(d.rtRp);
+    d.rt->build();
+
+    d.sampler = m_r->newSampler(QRhiSampler::Linear, QRhiSampler::Linear, QRhiSampler::None,
+                                QRhiSampler::ClampToEdge, QRhiSampler::ClampToEdge);
+    d.releasePool << d.sampler;
+    d.sampler->build();
+
+    d.srb = m_r->newShaderResourceBindings();
+    d.releasePool << d.srb;
+    d.srb->setBindings({
+        QRhiShaderResourceBinding::uniformBuffer(0, QRhiShaderResourceBinding::VertexStage | QRhiShaderResourceBinding::FragmentStage, d.ubuf),
+        QRhiShaderResourceBinding::sampledTexture(1, QRhiShaderResourceBinding::FragmentStage, d.tex, d.sampler)
+    });
+    d.srb->build();
+
+    d.ps = m_r->newGraphicsPipeline();
+    d.releasePool << d.ps;
+    d.ps->setShaderStages({
+        { QRhiGraphicsShaderStage::Vertex, getShader(QLatin1String(":/texture.vert.qsb")) },
+        { QRhiGraphicsShaderStage::Fragment, getShader(QLatin1String(":/texture.frag.qsb")) }
+    });
+    QRhiVertexInputLayout inputLayout;
+    inputLayout.setBindings({
+        { 4 * sizeof(float) }
+    });
+    inputLayout.setAttributes({
+        { 0, 0, QRhiVertexInputAttribute::Float2, 0 },
+        { 0, 1, QRhiVertexInputAttribute::Float2, 2 * sizeof(float) }
+    });
+    d.ps->setVertexInputLayout(inputLayout);
+    d.ps->setShaderResourceBindings(d.srb);
+    d.ps->setRenderPassDescriptor(m_rp);
+    d.ps->build();
+
+    d.initialUpdates = m_r->nextResourceUpdateBatch();
+    d.initialUpdates->uploadStaticBuffer(d.vbuf, 0, sizeof(quadVertexData), quadVertexData);
+    d.initialUpdates->uploadStaticBuffer(d.vbuf, sizeof(quadVertexData), sizeof(triangleData), triangleData);
+    d.initialUpdates->uploadStaticBuffer(d.ibuf, quadIndexData);
+
+    qint32 flip = m_r->isYUpInFramebuffer() ? 1 : 0;
+    d.initialUpdates->updateDynamicBuffer(d.ubuf, 64, 4, &flip);
+
+    // triangle
+    d.triUbuf = m_r->newBuffer(QRhiBuffer::Dynamic, QRhiBuffer::UniformBuffer, 68);
+    d.releasePool << d.triUbuf;
+    d.triUbuf->build();
+
+    d.triSrb = m_r->newShaderResourceBindings();
+    d.releasePool << d.triSrb;
+    d.triSrb->setBindings({
+        QRhiShaderResourceBinding::uniformBuffer(0, QRhiShaderResourceBinding::VertexStage | QRhiShaderResourceBinding::FragmentStage, d.triUbuf)
+    });
+    d.triSrb->build();
+
+    d.triPs = m_r->newGraphicsPipeline();
+    d.releasePool << d.triPs;
+    d.triPs->setShaderStages({
+        { QRhiGraphicsShaderStage::Vertex, getShader(QLatin1String(":/mrt.vert.qsb")) },
+        { QRhiGraphicsShaderStage::Fragment, getShader(QLatin1String(":/mrt.frag.qsb")) }
+    });
+    inputLayout.setBindings({
+        { 5 * sizeof(float) }
+    });
+    inputLayout.setAttributes({
+        { 0, 0, QRhiVertexInputAttribute::Float2, 0 },
+        { 0, 1, QRhiVertexInputAttribute::Float3, 2 * sizeof(float) }
+    });
+    d.triPs->setVertexInputLayout(inputLayout);
+    d.triPs->setShaderResourceBindings(d.triSrb);
+    d.triPs->setRenderPassDescriptor(d.rtRp);
+    d.triPs->build();
+
+    d.triBaseMvp = m_r->clipSpaceCorrMatrix();
+    d.triBaseMvp.perspective(45.0f, d.rt->sizeInPixels().width() / float(d.rt->sizeInPixels().height()), 0.01f, 1000.0f);
+    d.triBaseMvp.translate(0, 0, -2);
+    float opacity = 1.0f;
+    d.initialUpdates->updateDynamicBuffer(d.triUbuf, 64, 4, &opacity);
+}
+
+void Window::customRelease()
+{
+    for (QRhiResource *r : d.releasePool)
+        r->releaseAndDestroy();
+    d.releasePool.clear();
+}
+
+void Window::customRender()
+{
+    QRhiCommandBuffer *cb = m_sc->currentFrameCommandBuffer();
+    QRhiResourceUpdateBatch *u = m_r->nextResourceUpdateBatch();
+    if (d.initialUpdates) {
+        u->merge(d.initialUpdates);
+        d.initialUpdates->release();
+        d.initialUpdates = nullptr;
+    }
+
+    if (d.winProj != m_proj) {
+        d.winProj = m_proj;
+        QMatrix4x4 mvp = m_proj;
+        mvp.scale(2.5f);
+        u->updateDynamicBuffer(d.ubuf, 0, 64, mvp.constData());
+    }
+
+    QMatrix4x4 triMvp = d.triBaseMvp;
+    triMvp.rotate(d.triRot, 0, 1, 0);
+    d.triRot += 1;
+    u->updateDynamicBuffer(d.triUbuf, 0, 64, triMvp.constData());
+
+    cb->beginPass(d.rt, { 0.5f, 0.2f, 0, 1 }, { 1, 0 }, u);
+    cb->setGraphicsPipeline(d.triPs);
+    cb->setViewport({ 0, 0, float(d.rt->sizeInPixels().width()), float(d.rt->sizeInPixels().height()) });
+    cb->setShaderResources();
+    cb->setVertexInput(0, { { d.vbuf, sizeof(quadVertexData) } });
+    cb->draw(3);
+    cb->endPass();
+
+    const QSize outputSizeInPixels = m_sc->currentPixelSize();
+    cb->beginPass(m_sc->currentFrameRenderTarget(), { 0.4f, 0.7f, 0.0f, 1.0f }, { 1.0f, 0 });
+    cb->setGraphicsPipeline(d.ps);
+    cb->setViewport({ 0, 0, float(outputSizeInPixels.width()), float(outputSizeInPixels.height()) });
+    cb->setShaderResources();
+    cb->setVertexInput(0, { { d.vbuf, 0 } }, d.ibuf, 0, QRhiCommandBuffer::IndexUInt16);
+    cb->drawIndexed(6);
+    cb->endPass();
+}

examples/rhi/mrt/mrt.frag

+#version 440
+
+layout(location = 0) in vec3 v_color;
+
+layout(location = 0) out vec4 c0;
+layout(location = 1) out vec4 c1;
+layout(location = 2) out vec4 c2;
+layout(location = 3) out vec4 c3;
+
+layout(std140, binding = 0) uniform buf {
+    mat4 mvp;
+    float opacity;
+} ubuf;
+
+void main()
+{
+    vec4 c = vec4(v_color * ubuf.opacity, ubuf.opacity);
+    c0 = c;
+    c1 = c;
+    c2 = c;
+    c3 = c;
+}

examples/rhi/mrt/mrt.pro

+TEMPLATE = app
+
+QT += shadertools rhi
+
+SOURCES = \
+    mrt.cpp
+
+RESOURCES = mrt.qrc
+
+target.path = $$[QT_INSTALL_EXAMPLES]/rhi/mrt
+INSTALLS += target

examples/rhi/mrt/mrt.qrc

+<!DOCTYPE RCC><RCC version="1.0">
+  <qresource>
+    <file>mrt.vert.qsb</file>
+    <file>mrt.frag.qsb</file>
+    <file alias="texture.vert.qsb">../shared/texture.vert.qsb</file>
+    <file alias="texture.frag.qsb">../shared/texture.frag.qsb</file>
+</qresource>
+</RCC>

examples/rhi/mrt/mrt.vert

+#version 440
+
+layout(location = 0) in vec4 position;
+layout(location = 1) in vec3 color;
+
+layout(location = 0) out vec3 v_color;
+
+layout(std140, binding = 0) uniform buf {
+    mat4 mvp;
+    float opacity;
+} ubuf;
+
+out gl_PerVertex { vec4 gl_Position; };
+
+void main()
+{
+    v_color = color;
+    gl_Position = ubuf.mvp * position;
+}

examples/rhi/rhi.pro

@@ -13,7 +13,8 @@ SUBDIRS += \
     imguidemo \
     triquadcube \
     offscreen \
-    floattexture
+    floattexture \
+    mrt
 
 qtConfig(vulkan) {
     SUBDIRS += \

examples/rhi/triquadcube/triangleoncuberenderer.cpp

@@ -108,7 +108,7 @@ void TriangleOnCubeRenderer::initResources(QRhiRenderPassDescriptor *rp)
 
     if (DEPTH_TEXTURE) {
         m_offscreenTriangle.setDepthWrite(true);
-        m_depthTex = m_r->newTexture(QRhiTexture::D32, OFFSCREEN_SIZE, 1, QRhiTexture::RenderTarget);
+        m_depthTex = m_r->newTexture(QRhiTexture::D32F, OFFSCREEN_SIZE, 1, QRhiTexture::RenderTarget);
         m_depthTex->build();
     }
 

examples/rhi/triquadcube/triquadcube.cpp

@@ -166,8 +166,10 @@ void Window::customInit()
     qDebug("isFeatureSupported(NonDynamicUniformBuffers): %d", m_r->isFeatureSupported(QRhi::NonDynamicUniformBuffers));
     qDebug("isFeatureSupported(NonFourAlignedEffectiveIndexBufferOffset): %d", m_r->isFeatureSupported(QRhi::NonFourAlignedEffectiveIndexBufferOffset));
     qDebug("isFeatureSupported(NPOTTextureRepeat): %d", m_r->isFeatureSupported(QRhi::NPOTTextureRepeat));
-    qDebug("Min 2D texture width/height: %d", m_r->resourceSizeLimit(QRhi::TextureSizeMin));
-    qDebug("Max 2D texture width/height: %d", m_r->resourceSizeLimit(QRhi::TextureSizeMax));
+    qDebug("isFeatureSupported(RedOrAlpha8IsRed): %d", m_r->isFeatureSupported(QRhi::RedOrAlpha8IsRed));
+    qDebug("Min 2D texture width/height: %d", m_r->resourceLimit(QRhi::TextureSizeMin));
+    qDebug("Max 2D texture width/height: %d", m_r->resourceLimit(QRhi::TextureSizeMax));
+    qDebug("Max color attachment count: %d", m_r->resourceLimit(QRhi::MaxColorAttachments));
 }
 
 void Window::customRelease()

src/rhi/qrhi.cpp

@@ -431,7 +431,7 @@ QT_BEGIN_NAMESPACE
  */
 
 /*!
-    \enum QRhi::ResourceSizeLimit
+    \enum QRhi::ResourceLimit
     Describes the resource limit to query.
 
     \value TextureSizeMin Minimum texture width and height. This is typically
@@ -443,6 +443,12 @@ QT_BEGIN_NAMESPACE
     graphics API and sometimes the platform or implementation as well.
     Typically the value is in the range 4096 - 16384. Attempting to create
     textures larger than this is expected to fail.
+
+    \value MaxColorAttachments The maximum number of color attachments for a
+    QRhiTextureRenderTarget, in case multiple render targets are supported. When
+    MRT is not supported, the value is 1. Otherwise this is typically 8, but
+    watch out for the fact that OpenGL only mandates 4 as the minimum, and that
+    is what some OpenGL ES implementations provide.
  */
 
 /*!
@@ -4126,9 +4132,9 @@ bool QRhi::isFeatureSupported(QRhi::Feature feature) const
     The values are expected to be queried by the backends upon initialization,
     meaning calling this function is a light operation.
  */
-int QRhi::resourceSizeLimit(ResourceSizeLimit limit) const
+int QRhi::resourceLimit(ResourceLimit limit) const
 {
-    return d->resourceSizeLimit(limit);
+    return d->resourceLimit(limit);
 }
 
 /*!

src/rhi/qrhi.h

@@ -1254,9 +1254,10 @@ public:
     };
     Q_DECLARE_FLAGS(EndFrameFlags, EndFrameFlag)
 
-    enum ResourceSizeLimit {
+    enum ResourceLimit {
         TextureSizeMin = 1,
-        TextureSizeMax
+        TextureSizeMax,
+        MaxColorAttachments
     };
 
     ~QRhi();
@@ -1319,7 +1320,7 @@ public:
 
     bool isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags = QRhiTexture::Flags()) const;
     bool isFeatureSupported(QRhi::Feature feature) const;
-    int resourceSizeLimit(ResourceSizeLimit limit) const;
+    int resourceLimit(ResourceLimit limit) const;
 
     const QRhiNativeHandles *nativeHandles();
 

src/rhi/qrhi_p.h

@@ -133,7 +133,7 @@ public:
     virtual QMatrix4x4 clipSpaceCorrMatrix() const = 0;
     virtual bool isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags) const = 0;
     virtual bool isFeatureSupported(QRhi::Feature feature) const = 0;
-    virtual int resourceSizeLimit(QRhi::ResourceSizeLimit limit) const = 0;
+    virtual int resourceLimit(QRhi::ResourceLimit limit) const = 0;
     virtual const QRhiNativeHandles *nativeHandles() = 0;
 
     virtual void sendVMemStatsToProfiler();

src/rhi/qrhid3d11.cpp

@@ -365,13 +365,15 @@ bool QRhiD3D11::isFeatureSupported(QRhi::Feature feature) const
     }
 }
 
-int QRhiD3D11::resourceSizeLimit(QRhi::ResourceSizeLimit limit) const
+int QRhiD3D11::resourceLimit(QRhi::ResourceLimit limit) const
 {
     switch (limit) {
     case QRhi::TextureSizeMin:
         return 1;
     case QRhi::TextureSizeMax:
         return D3D11_REQ_TEXTURE2D_U_OR_V_DIMENSION;
+    case QRhi::MaxColorAttachments:
+        return 8;
     default:
         Q_UNREACHABLE();
         return 0;

src/rhi/qrhid3d11_p.h

@@ -535,7 +535,7 @@ public:
     QMatrix4x4 clipSpaceCorrMatrix() const override;
     bool isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags) const override;
     bool isFeatureSupported(QRhi::Feature feature) const override;
-    int resourceSizeLimit(QRhi::ResourceSizeLimit limit) const override;
+    int resourceLimit(QRhi::ResourceLimit limit) const override;
     const QRhiNativeHandles *nativeHandles() override;
 
     void enqueueResourceUpdates(QRhiCommandBuffer *cb, QRhiResourceUpdateBatch *resourceUpdates);

src/rhi/qrhigles2.cpp

@@ -196,6 +196,10 @@ QT_BEGIN_NAMESPACE
 #define GL_FRAMEBUFFER_SRGB 0x8DB9
 #endif
 
+#ifndef GL_MAX_DRAW_BUFFERS
+#define GL_MAX_DRAW_BUFFERS               0x8824
+#endif
+
 static QSurfaceFormat qrhigles2_effectiveFormat()
 {
     QSurfaceFormat fmt = QSurfaceFormat::defaultFormat();
@@ -297,6 +301,8 @@ bool QRhiGles2::create(QRhi::Flags flags)
     if (vendor && renderer && version)
         qDebug("OpenGL VENDOR: %s RENDERER: %s VERSION: %s", vendor, renderer, version);
 
+    const QSurfaceFormat actualFormat = ctx->format();
+
     GLint n = 0;
     f->glGetIntegerv(GL_NUM_COMPRESSED_TEXTURE_FORMATS, &n);
     supportedCompressedFormats.resize(n);
@@ -305,13 +311,17 @@ bool QRhiGles2::create(QRhi::Flags flags)
 
     f->glGetIntegerv(GL_MAX_TEXTURE_SIZE, &caps.maxTextureSize);
 
+    if (actualFormat.renderableType() == QSurfaceFormat::OpenGL || actualFormat.version() >= qMakePair(3, 0))
+        f->glGetIntegerv(GL_MAX_DRAW_BUFFERS, &caps.maxDrawBuffers);
+    else
+        caps.maxDrawBuffers = 1;
+
     caps.msaaRenderBuffer = f->hasOpenGLExtension(QOpenGLExtensions::FramebufferMultisample)
             && f->hasOpenGLExtension(QOpenGLExtensions::FramebufferBlit);
 
     caps.npotTexture = f->hasOpenGLFeature(QOpenGLFunctions::NPOTTextures);
     caps.npotTextureRepeat = f->hasOpenGLFeature(QOpenGLFunctions::NPOTTextureRepeat);
 
-    const QSurfaceFormat actualFormat = ctx->format();
     if (actualFormat.renderableType() == QSurfaceFormat::OpenGLES)
         caps.fixedIndexPrimitiveRestart = actualFormat.version() >= qMakePair(3, 0);
     else
@@ -532,13 +542,15 @@ bool QRhiGles2::isFeatureSupported(QRhi::Feature feature) const
     }
 }
 
-int QRhiGles2::resourceSizeLimit(QRhi::ResourceSizeLimit limit) const
+int QRhiGles2::resourceLimit(QRhi::ResourceLimit limit) const
 {
     switch (limit) {
     case QRhi::TextureSizeMin:
         return 1;
     case QRhi::TextureSizeMax:
         return caps.maxTextureSize;
+    case QRhi::MaxColorAttachments:
+        return caps.maxDrawBuffers;
     default:
         Q_UNREACHABLE();
         return 0;

src/rhi/qrhigles2_p.h

@@ -534,7 +534,7 @@ public:
     QMatrix4x4 clipSpaceCorrMatrix() const override;
     bool isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags) const override;
     bool isFeatureSupported(QRhi::Feature feature) const override;
-    int resourceSizeLimit(QRhi::ResourceSizeLimit limit) const override;
+    int resourceLimit(QRhi::ResourceLimit limit) const override;
     const QRhiNativeHandles *nativeHandles() override;
 
     bool ensureContext(QSurface *surface = nullptr) const;
@@ -554,6 +554,7 @@ public:
     struct Caps {
         Caps()
             : maxTextureSize(2048),
+              maxDrawBuffers(4),
               msaaRenderBuffer(false),
               npotTexture(true),
               npotTextureRepeat(true),
@@ -567,6 +568,7 @@ public:
               srgbCapableDefaultFramebuffer(false)
         { }
         int maxTextureSize;
+        int maxDrawBuffers;
         // Multisample fb and blit are supported (GLES 3.0 or OpenGL 3.x). Not
         // the same as multisample textures!
         uint msaaRenderBuffer : 1;

src/rhi/qrhimetal.mm

@@ -484,13 +484,15 @@ bool QRhiMetal::isFeatureSupported(QRhi::Feature feature) const
     }
 }
 
-int QRhiMetal::resourceSizeLimit(QRhi::ResourceSizeLimit limit) const
+int QRhiMetal::resourceLimit(QRhi::ResourceLimit limit) const
 {
     switch (limit) {
     case QRhi::TextureSizeMin:
         return 1;
     case QRhi::TextureSizeMax:
         return caps.maxTextureSize;
+    case QRhi::MaxColorAttachments:
+        return 8;
     default:
         Q_UNREACHABLE();
         return 0;

src/rhi/qrhimetal_p.h

@@ -357,7 +357,7 @@ public:
     QMatrix4x4 clipSpaceCorrMatrix() const override;
     bool isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags) const override;
     bool isFeatureSupported(QRhi::Feature feature) const override;
-    int resourceSizeLimit(QRhi::ResourceSizeLimit limit) const override;
+    int resourceLimit(QRhi::ResourceLimit limit) const override;
     const QRhiNativeHandles *nativeHandles() override;
 
     void executeDeferredReleases(bool forced = false);

src/rhi/qrhinull.cpp

@@ -133,13 +133,15 @@ bool QRhiNull::isFeatureSupported(QRhi::Feature feature) const
     return true;
 }
 
-int QRhiNull::resourceSizeLimit(QRhi::ResourceSizeLimit limit) const
+int QRhiNull::resourceLimit(QRhi::ResourceLimit limit) const
 {
     switch (limit) {
     case QRhi::TextureSizeMin:
         return 1;
     case QRhi::TextureSizeMax:
         return 16384;
+    case QRhi::MaxColorAttachments:
+        return 8;
     default:
         Q_UNREACHABLE();
         return 0;

src/rhi/qrhinull_p.h

@@ -243,7 +243,7 @@ public:
     QMatrix4x4 clipSpaceCorrMatrix() const override;
     bool isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags) const override;
     bool isFeatureSupported(QRhi::Feature feature) const override;
-    int resourceSizeLimit(QRhi::ResourceSizeLimit limit) const override;
+    int resourceLimit(QRhi::ResourceLimit limit) const override;
     const QRhiNativeHandles *nativeHandles() override;
 
     QRhiNullNativeHandles nativeHandlesStruct;

src/rhi/qrhivulkan.cpp

@@ -2976,13 +2976,15 @@ bool QRhiVulkan::isFeatureSupported(QRhi::Feature feature) const
     }
 }
 
-int QRhiVulkan::resourceSizeLimit(QRhi::ResourceSizeLimit limit) const
+int QRhiVulkan::resourceLimit(QRhi::ResourceLimit limit) const
 {
     switch (limit) {
     case QRhi::TextureSizeMin:
         return 1;
     case QRhi::TextureSizeMax:
         return physDevProperties.limits.maxImageDimension2D;
+    case QRhi::MaxColorAttachments:
+        return physDevProperties.limits.maxColorAttachments;
     default:
         Q_UNREACHABLE();
         return 0;

src/rhi/qrhivulkan_p.h

@@ -428,7 +428,7 @@ public:
     QMatrix4x4 clipSpaceCorrMatrix() const override;
     bool isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags) const override;
     bool isFeatureSupported(QRhi::Feature feature) const override;
-    int resourceSizeLimit(QRhi::ResourceSizeLimit limit) const override;
+    int resourceLimit(QRhi::ResourceLimit limit) const override;
     const QRhiNativeHandles *nativeHandles() override;
     void sendVMemStatsToProfiler() override;