Add an initial rhi implementation that mimics the opengl implementation

common/rhi/shaders/flow.vert

@@ -0,0 +1,59 @@
+#version 450
+
+// Per-vertex attributes
+layout(location = 0) in vec3 position;
+layout(location = 1) in vec2 texCoord;
+
+// Per-instance attributes (mat4 split into 4 vec4s for better D3D11 compatibility)
+layout(location = 2) in vec4 instanceModel_row0;
+layout(location = 3) in vec4 instanceModel_row1;
+layout(location = 4) in vec4 instanceModel_row2;
+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;
+
+// Outputs to fragment shader
+layout(location = 0) out vec2 vTexCoord;
+layout(location = 1) out vec4 vColor;
+layout(location = 2) out float vIsReflection;
+
+// Uniform buffer
+layout(std140, binding = 0) uniform UniformBuffer
+{
+    mat4 viewProjectionMatrix;
+    vec3 backgroundColor;
+    float _pad0;
+    vec3 shadingColor;
+    float _pad1;
+    float reflectionUp;
+    float reflectionDown;
+    int isReflection;
+    float _pad2;
+};
+
+void main()
+{
+    // Reconstruct instance model matrix from 4 vec4 rows
+    mat4 instanceModel = mat4(instanceModel_row0, instanceModel_row1, instanceModel_row2, instanceModel_row3);
+
+    gl_Position = viewProjectionMatrix * instanceModel * vec4(position, 1.0);
+    vTexCoord = texCoord;
+
+    // Flip texture vertically per-instance when requested (reflection)
+    if (instanceFlip != 0.0) {
+        vTexCoord.y = 1.0 - texCoord.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);
+    vIsReflection = instanceFlip;
+}