Add an rt flag to preserve depth-stencil

src/rhi/qrhi.h

@@ -606,7 +606,8 @@ class Q_RHI_EXPORT QRhiTextureRenderTarget : public QRhiRenderTarget
 {
 public:
     enum Flag {
-        PreserveColorContents = 1 << 0
+        PreserveColorContents = 1 << 0,
+        PreserveDepthStencilContents = 1 << 1
     };
     Q_DECLARE_FLAGS(Flags, Flag)
 

src/rhi/qrhid3d11.cpp

@@ -978,10 +978,12 @@ void QRhiD3D11::beginPass(QRhiCommandBuffer *cb,
 
     QD3D11CommandBuffer *cbD = QRHI_RES(QD3D11CommandBuffer, cb);
     bool needsColorClear = true;
+    bool needsDsClear = true;
     QD3D11RenderTargetData *rtD = rtData(rt);
     if (rt->type() == QRhiRenderTarget::RtTexture) {
         QD3D11TextureRenderTarget *rtTex = QRHI_RES(QD3D11TextureRenderTarget, rt);
         needsColorClear = !rtTex->m_flags.testFlag(QRhiTextureRenderTarget::PreserveColorContents);
+        needsDsClear = !rtTex->m_flags.testFlag(QRhiTextureRenderTarget::PreserveDepthStencilContents);
     }
 
     cbD->currentTarget = rt;
@@ -995,12 +997,10 @@ void QRhiD3D11::beginPass(QRhiCommandBuffer *cb,
     clearCmd.cmd = QD3D11CommandBuffer::Command::Clear;
     clearCmd.args.clear.rt = rt;
     clearCmd.args.clear.mask = 0;
-    if (!rtD->colorAttCount)
-        needsColorClear = false;
-    if (rtD->dsAttCount)
-        clearCmd.args.clear.mask |= QD3D11CommandBuffer::Command::Depth | QD3D11CommandBuffer::Command::Stencil;
-    if (needsColorClear)
+    if (rtD->colorAttCount && needsColorClear)
         clearCmd.args.clear.mask |= QD3D11CommandBuffer::Command::Color;
+    if (rtD->dsAttCount && needsDsClear)
+        clearCmd.args.clear.mask |= QD3D11CommandBuffer::Command::Depth | QD3D11CommandBuffer::Command::Stencil;
 
     memcpy(clearCmd.args.clear.c, &colorClearValue.rgba, sizeof(float) * 4);
     clearCmd.args.clear.d = depthStencilClearValue.d;

src/rhi/qrhigles2.cpp

@@ -1377,6 +1377,7 @@ void QRhiGles2::beginPass(QRhiCommandBuffer *cb,
 
     QGles2CommandBuffer *cbD = QRHI_RES(QGles2CommandBuffer, cb);
     bool needsColorClear = true;
+    bool needsDsClear = true;
     QGles2BasicRenderTargetData *rtD = nullptr;
     QGles2CommandBuffer::Command fbCmd;
     fbCmd.cmd = QGles2CommandBuffer::Command::BindFramebuffer;
@@ -1390,6 +1391,7 @@ void QRhiGles2::beginPass(QRhiCommandBuffer *cb,
         QGles2TextureRenderTarget *rtTex = QRHI_RES(QGles2TextureRenderTarget, rt);
         rtD = &rtTex->d;
         needsColorClear = !rtTex->m_flags.testFlag(QRhiTextureRenderTarget::PreserveColorContents);
+        needsDsClear = !rtTex->m_flags.testFlag(QRhiTextureRenderTarget::PreserveDepthStencilContents);
         fbCmd.args.bindFramebuffer.rt = rtTex;
     }
         break;
@@ -1405,10 +1407,10 @@ void QRhiGles2::beginPass(QRhiCommandBuffer *cb,
     QGles2CommandBuffer::Command clearCmd;
     clearCmd.cmd = QGles2CommandBuffer::Command::Clear;
     clearCmd.args.clear.mask = 0;
-    if (rtD->attCount > 1)
-        clearCmd.args.clear.mask |= GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT;
-    if (needsColorClear)
+    if (rtD->attCount > 0 && needsColorClear)
         clearCmd.args.clear.mask |= GL_COLOR_BUFFER_BIT;
+    if (rtD->attCount > 1 && needsDsClear)
+        clearCmd.args.clear.mask |= GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT;
 
     memcpy(clearCmd.args.clear.c, &colorClearValue.rgba, sizeof(float) * 4);
     clearCmd.args.clear.d = depthStencilClearValue.d;

src/rhi/qrhimetal.mm

@@ -1046,17 +1046,21 @@ void QRhiMetal::beginPass(QRhiCommandBuffer *cb,
     switch (rt->type()) {
     case QRhiRenderTarget::RtRef:
         rtD = QRHI_RES(QMetalReferenceRenderTarget, rt)->d;
-        cbD->d->currentPassRpDesc = d->createDefaultRenderPass(false, colorClearValue, depthStencilClearValue);
+        cbD->d->currentPassRpDesc = d->createDefaultRenderPass(rtD->dsAttCount, colorClearValue, depthStencilClearValue);
         break;
     case QRhiRenderTarget::RtTexture:
     {
         QMetalTextureRenderTarget *rtTex = QRHI_RES(QMetalTextureRenderTarget, rt);
         rtD = rtTex->d;
-        cbD->d->currentPassRpDesc = d->createDefaultRenderPass(false, colorClearValue, depthStencilClearValue);
+        cbD->d->currentPassRpDesc = d->createDefaultRenderPass(rtD->dsAttCount, colorClearValue, depthStencilClearValue);
         if (rtTex->m_flags.testFlag(QRhiTextureRenderTarget::PreserveColorContents)) {
             for (int i = 0; i < rtD->colorAttCount; ++i)
                 cbD->d->currentPassRpDesc.colorAttachments[i].loadAction = MTLLoadActionLoad;
         }
+        if (rtD->dsAttCount && rtTex->m_flags.testFlag(QRhiTextureRenderTarget::PreserveDepthStencilContents)) {
+            cbD->d->currentPassRpDesc.depthAttachment.loadAction = MTLLoadActionLoad;
+            cbD->d->currentPassRpDesc.stencilAttachment.loadAction = MTLLoadActionLoad;
+        }
     }
         break;
     default:

src/rhi/qrhivulkan.cpp

@@ -795,6 +795,7 @@ bool QRhiVulkan::createDefaultRenderPass(VkRenderPass *rp, bool hasDepthStencil,
 bool QRhiVulkan::createOffscreenRenderPass(VkRenderPass *rp,
                                            const QVector<QRhiTextureRenderTargetDescription::ColorAttachment> &colorAttachments,
                                            bool preserveColor,
+                                           bool preserveDs,
                                            QRhiRenderBuffer *depthStencilBuffer,
                                            QRhiTexture *depthTexture)
 {
@@ -834,14 +835,16 @@ bool QRhiVulkan::createOffscreenRenderPass(VkRenderPass *rp,
                                                : QRHI_RES(QVkRenderBuffer, depthStencilBuffer)->vkformat;
         const VkSampleCountFlagBits samples = depthTexture ? QRHI_RES(QVkTexture, depthTexture)->samples
                                                            : QRHI_RES(QVkRenderBuffer, depthStencilBuffer)->samples;
+        const VkAttachmentLoadOp loadOp = preserveDs ? VK_ATTACHMENT_LOAD_OP_LOAD : VK_ATTACHMENT_LOAD_OP_CLEAR;
+        const VkAttachmentStoreOp storeOp = depthTexture ? VK_ATTACHMENT_STORE_OP_STORE : VK_ATTACHMENT_STORE_OP_DONT_CARE;
         VkAttachmentDescription attDesc;
         memset(&attDesc, 0, sizeof(attDesc));
         attDesc.format = dsFormat;
         attDesc.samples = samples;
-        attDesc.loadOp = VK_ATTACHMENT_LOAD_OP_CLEAR;
-        attDesc.storeOp = depthTexture ? VK_ATTACHMENT_STORE_OP_STORE : VK_ATTACHMENT_STORE_OP_DONT_CARE;
-        attDesc.stencilLoadOp = VK_ATTACHMENT_LOAD_OP_CLEAR;
-        attDesc.stencilStoreOp = depthTexture ? VK_ATTACHMENT_STORE_OP_STORE : VK_ATTACHMENT_STORE_OP_DONT_CARE;
+        attDesc.loadOp = loadOp;
+        attDesc.storeOp = storeOp;
+        attDesc.stencilLoadOp = loadOp;
+        attDesc.stencilStoreOp = storeOp;
         attDesc.initialLayout = VK_IMAGE_LAYOUT_UNDEFINED;
         attDesc.finalLayout = depthTexture ? VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL : VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL;
         attDescs.append(attDesc);
@@ -3625,6 +3628,7 @@ QRhiRenderPassDescriptor *QVkTextureRenderTarget::newCompatibleRenderPassDescrip
     if (!rhiD->createOffscreenRenderPass(&rp->rp,
                                          m_desc.colorAttachments,
                                          m_flags.testFlag(QRhiTextureRenderTarget::PreserveColorContents),
+                                         m_flags.testFlag(QRhiTextureRenderTarget::PreserveDepthStencilContents),
                                          m_desc.depthStencilBuffer,
                                          m_desc.depthTexture))
     {

src/rhi/qrhivulkan_p.h

@@ -406,6 +406,7 @@ public:
     bool createOffscreenRenderPass(VkRenderPass *rp,
                                    const QVector<QRhiTextureRenderTargetDescription::ColorAttachment> &colorAttachments,
                                    bool preserveColor,
+                                   bool preserveDs,
                                    QRhiRenderBuffer *depthStencilBuffer,
                                    QRhiTexture *depthTexture);
     bool ensurePipelineCache();