Use the fragment shader to calculate the shading effect for a more uniform shading than the one based on vertex

common/rhi/shaders/flow.frag

@@ -2,8 +2,11 @@
 
 // Inputs from vertex shader
 layout(location = 0) in vec2 vTexCoord;
-layout(location = 1) in vec4 vColor;
-layout(location = 2) in float vIsReflection;
+layout(location = 1) in flat vec4 vInstanceShading;
+layout(location = 2) in flat float vInstanceOpacity;
+layout(location = 3) in flat float vIsReflection;
+layout(location = 4) in flat float vInstanceRotation;
+layout(location = 5) in vec2 vLocalPos;
 
 // Output
 layout(location = 0) out vec4 fragColor;
@@ -29,16 +32,30 @@ void main()
 {
     vec4 texColor = texture(coverTexture, vTexCoord);
 
-    // Apply shading: multiply texture by vColor.r to darken
-    float shadingAmount = vColor.r;
+    // Compute per-pixel shading using per-instance corner shading values
+    float leftUp = vInstanceShading.x;
+    float leftDown = vInstanceShading.y;
+    float rightUp = vInstanceShading.z;
+    float rightDown = vInstanceShading.w;
 
-    // For reflections, apply gradient fade (darker at bottom, fading to black)
+    // Use interpolated local vertex position to match original vertex-based shading.
+    // position.y in vertex ranges [-0.5..0.5], so map to [0..1] with +0.5
+    float y = clamp(vLocalPos.y + 0.5, 0.0, 1.0);
+    float x = clamp(vLocalPos.x + 0.5, 0.0, 1.0);
+    float leftShading = mix(leftDown, leftUp, y);
+    float rightShading = mix(rightDown, rightUp, y);
+    float shading = mix(leftShading, rightShading, x);
+
+    // Combine with per-instance opacity (opacity only darkens RGB, alpha preserved)
+    float shadingAmount = shading * vInstanceOpacity;
+
+    // For reflections, apply a gradient fade using reflection uniforms (darker further away)
     if (vIsReflection > 0.5) {
-        // vTexCoord.y goes from 1 (top of reflection, near cover) to 0 (bottom, far from cover)
-        // We want it brightest near the cover and fading away
+        // Legacy reflection fade: ramp from 0.0 to 0.33 using texture V coordinate
         float gradientFade = mix(0.0, 0.33, vTexCoord.y);
         shadingAmount *= gradientFade;
     }
 
+    // Final color: shaded RGB, keep source alpha
     fragColor = vec4(texColor.rgb * shadingAmount, texColor.a);
 }

common/rhi/shaders/flow.vert

@@ -12,11 +12,15 @@ layout(location = 5) in vec4 instanceModel_row3;
 layout(location = 6) in vec4 instanceShading1;
 layout(location = 7) in float instanceOpacity;
 layout(location = 8) in float instanceFlip;
+layout(location = 9) in float instanceRotation;
 
 // Outputs to fragment shader
 layout(location = 0) out vec2 vTexCoord;
-layout(location = 1) out vec4 vColor;
-layout(location = 2) out float vIsReflection;
+layout(location = 1) out flat vec4 vInstanceShading;
+layout(location = 2) out flat float vInstanceOpacity;
+layout(location = 3) out flat float vIsReflection;
+layout(location = 4) out flat float vInstanceRotation;
+layout(location = 5) out vec2 vLocalPos;
 
 // Uniform buffer
 layout(std140, binding = 0) uniform UniformBuffer
@@ -39,21 +43,16 @@ void main()
 
     gl_Position = viewProjectionMatrix * instanceModel * vec4(position, 1.0);
     vTexCoord = texCoord;
+    vLocalPos = position.xy;
 
     // Flip texture vertically per-instance when requested (reflection)
     if (instanceFlip != 0.0) {
-        vTexCoord.y = 1.0 - texCoord.y;
+        vTexCoord.y = 1.0 - vTexCoord.y;
     }
 
-    float leftUpShading = instanceShading1.x;
-    float leftDownShading = instanceShading1.y;
-    float rightUpShading = instanceShading1.z;
-    float rightDownShading = instanceShading1.w;
-
-    float leftShading = mix(leftDownShading, leftUpShading, (position.y + 0.5));
-    float rightShading = mix(rightDownShading, rightUpShading, (position.y + 0.5));
-    float shading = mix(leftShading, rightShading, (position.x + 0.5));
-
-    vColor = vec4(shading * instanceOpacity);
+    // Pass per-instance values to fragment shader as flat (no interpolation)
+    vInstanceShading = instanceShading1;
+    vInstanceOpacity = instanceOpacity;
     vIsReflection = instanceFlip;
+    vInstanceRotation = instanceRotation;
 }

common/rhi/yacreader_flow_rhi.cpp

@@ -194,9 +194,9 @@ void YACReaderFlow3D::initialize(QRhiCommandBuffer *cb)
 
     // Create instance buffer for per-draw instance data
     if (!scene.instanceBuffer) {
-        // Allocate buffer for per-instance data (model matrix + shading + opacity + flipFlag)
-        // mat4 (16 floats) + vec4 (4 floats) + float (1 float) + float (1 float) = 22 floats
-        scene.instanceBuffer.reset(m_rhi->newBuffer(QRhiBuffer::Dynamic, QRhiBuffer::VertexBuffer, 22 * sizeof(float)));
+        // Allocate buffer for per-instance data (model matrix + shading + opacity + flipFlag + rotation)
+        // mat4 (16 floats) + vec4 (4 floats) + float (opacity) + float (flipFlag) + float (rotation) = 23 floats
+        scene.instanceBuffer.reset(m_rhi->newBuffer(QRhiBuffer::Dynamic, QRhiBuffer::VertexBuffer, 23 * sizeof(float)));
         scene.instanceBuffer->create();
     }
 
@@ -333,7 +333,7 @@ void YACReaderFlow3D::ensurePipeline()
     QRhiVertexInputLayout inputLayout;
     inputLayout.setBindings({
             { 5 * sizeof(float) }, // Per-vertex data (position + texCoord)
-            { 22 * sizeof(float), QRhiVertexInputBinding::PerInstance } // Per-instance data
+            { 23 * sizeof(float), QRhiVertexInputBinding::PerInstance } // Per-instance data
     });
     inputLayout.setAttributes({
             // Per-vertex attributes
@@ -347,7 +347,8 @@ void YACReaderFlow3D::ensurePipeline()
             { 1, 5, QRhiVertexInputAttribute::Float4, 12 * sizeof(float) }, // row 3
             { 1, 6, QRhiVertexInputAttribute::Float4, 16 * sizeof(float) }, // shading vec4
             { 1, 7, QRhiVertexInputAttribute::Float, 20 * sizeof(float) }, // opacity
-            { 1, 8, QRhiVertexInputAttribute::Float, 21 * sizeof(float) } // flipFlag (1.0 = reflection)
+            { 1, 8, QRhiVertexInputAttribute::Float, 21 * sizeof(float) }, // flipFlag (1.0 = reflection)
+            { 1, 9, QRhiVertexInputAttribute::Float, 22 * sizeof(float) } // rotation
     });
     scene.pipeline->setVertexInputLayout(inputLayout);
 
@@ -408,7 +409,7 @@ void YACReaderFlow3D::render(QRhiCommandBuffer *cb)
         bool isReflection;
         bool isMark;
         QRhiTexture *texture;
-        float instanceData[22];
+        float instanceData[23];
         UniformData uniformData;
     };
 
@@ -482,7 +483,7 @@ void YACReaderFlow3D::render(QRhiCommandBuffer *cb)
     }
 
     // Ensure instance buffer is large enough for all draws
-    auto requiredInstanceSize = static_cast<quint32>(draws.size() * 22 * sizeof(float));
+    auto requiredInstanceSize = static_cast<quint32>(draws.size() * 23 * sizeof(float));
     if (!scene.instanceBuffer || scene.instanceBuffer->size() < requiredInstanceSize) {
         scene.instanceBuffer.reset(m_rhi->newBuffer(QRhiBuffer::Dynamic, QRhiBuffer::VertexBuffer, requiredInstanceSize));
         if (!scene.instanceBuffer->create()) {
@@ -514,8 +515,8 @@ void YACReaderFlow3D::render(QRhiCommandBuffer *cb)
 
     // Update instance buffer with all instance data
     for (int i = 0; i < draws.size(); ++i) {
-        int offset = i * 22 * sizeof(float);
-        batch->updateDynamicBuffer(scene.instanceBuffer.get(), offset, 22 * sizeof(float), draws[i].instanceData);
+        int offset = i * 23 * sizeof(float);
+        batch->updateDynamicBuffer(scene.instanceBuffer.get(), offset, 23 * sizeof(float), draws[i].instanceData);
     }
 
     // === PHASE 2: RENDER (DURING PASS) ===
@@ -601,6 +602,9 @@ void YACReaderFlow3D::prepareDrawData(const YACReader3DImageRHI &image, bool isR
         outInstanceData[i] = matData[i];
     }
 
+    // Store per-instance rotation in the instance data (new slot at index 22)
+    outInstanceData[22] = image.current.rot;
+
     // Prepare uniform data
     outUniformData.viewProjectionMatrix = viewProjectionMatrix;
     outUniformData.backgroundColor = QVector3D(backgroundColor.redF(), backgroundColor.greenF(), backgroundColor.blueF());
@@ -637,7 +641,7 @@ void YACReaderFlow3D::executeDrawWithOffset(QRhiCommandBuffer *cb, QRhiTexture *
     // Bind vertex buffers with offset into instance buffer
     const QRhiCommandBuffer::VertexInput vbufBindings[] = {
         { scene.vertexBuffer.get(), 0 },
-        { scene.instanceBuffer.get(), quint32(uniformSlot * 22 * sizeof(float)) }
+        { scene.instanceBuffer.get(), quint32(uniformSlot * 23 * sizeof(float)) }
     };
     cb->setVertexInput(0, 2, vbufBindings);