Fix RHI constant binding and add sphere test

tests/RHI/unit/test_descriptor_set.cpp

@@ -493,3 +493,57 @@ TEST_P(RHITestFixture, DescriptorSet_Update_UsesBindingNumberOnOpenGL) {
     pool->Shutdown();
     delete pool;
 }
+
+TEST_P(RHITestFixture, DescriptorSet_BindConstantBuffer_UsesBindingNumberOnOpenGL) {
+    if (GetBackendType() != RHIType::OpenGL) {
+        GTEST_SKIP() << "OpenGL-specific constant buffer binding verification";
+    }
+
+    auto* openGLDevice = static_cast<OpenGLDevice*>(GetDevice());
+    ASSERT_NE(openGLDevice, nullptr);
+    ASSERT_TRUE(openGLDevice->MakeContextCurrent());
+
+    DescriptorPoolDesc poolDesc = {};
+    poolDesc.type = DescriptorHeapType::CBV_SRV_UAV;
+    poolDesc.descriptorCount = 1;
+    poolDesc.shaderVisible = false;
+
+    RHIDescriptorPool* pool = GetDevice()->CreateDescriptorPool(poolDesc);
+    ASSERT_NE(pool, nullptr);
+
+    DescriptorSetLayoutBinding binding = {};
+    binding.binding = 3;
+    binding.type = static_cast<uint32_t>(DescriptorType::CBV);
+    binding.count = 1;
+
+    DescriptorSetLayoutDesc layoutDesc = {};
+    layoutDesc.bindings = &binding;
+    layoutDesc.bindingCount = 1;
+
+    RHIDescriptorSet* set = pool->AllocateSet(layoutDesc);
+    ASSERT_NE(set, nullptr);
+
+    const float matrixData[16] = {
+        1.0f, 0.0f, 0.0f, 0.0f,
+        0.0f, 1.0f, 0.0f, 0.0f,
+        0.0f, 0.0f, 1.0f, 0.0f,
+        0.0f, 0.0f, 0.0f, 1.0f,
+    };
+    set->WriteConstant(3, matrixData, sizeof(matrixData));
+    set->Bind();
+
+    GLint boundBuffer = 0;
+    glGetIntegeri_v(GL_UNIFORM_BUFFER_BINDING, 3, &boundBuffer);
+    EXPECT_NE(boundBuffer, 0);
+
+    set->Unbind();
+
+    GLint unboundBuffer = -1;
+    glGetIntegeri_v(GL_UNIFORM_BUFFER_BINDING, 3, &unboundBuffer);
+    EXPECT_EQ(unboundBuffer, 0);
+
+    set->Shutdown();
+    delete set;
+    pool->Shutdown();
+    delete pool;
+}

tests/RHI/unit/test_pipeline_layout.cpp

@@ -1,4 +1,5 @@
 #include "fixtures/RHITestFixture.h"
+#include "XCEngine/RHI/D3D12/D3D12PipelineLayout.h"
 #include "XCEngine/RHI/RHIPipelineLayout.h"
 #include "XCEngine/RHI/RHIDescriptorSet.h"
 
@@ -151,4 +152,28 @@ TEST_P(RHITestFixture, PipelineLayout_DescriptorSetAllocation) {
 
     layout->Shutdown();
     delete layout;
-}
+}
+
+TEST_P(RHITestFixture, PipelineLayout_D3D12ConstantBuffers_MapToDistinctRootParameters) {
+    if (GetBackendType() != RHIType::D3D12) {
+        GTEST_SKIP() << "D3D12-specific root parameter verification";
+    }
+
+    RHIPipelineLayoutDesc desc = {};
+    desc.constantBufferCount = 2;
+    desc.textureCount = 1;
+    desc.samplerCount = 1;
+
+    RHIPipelineLayout* layout = GetDevice()->CreatePipelineLayout(desc);
+    ASSERT_NE(layout, nullptr);
+
+    auto* d3d12Layout = static_cast<D3D12PipelineLayout*>(layout);
+    EXPECT_TRUE(d3d12Layout->HasRootParameter(0));
+    EXPECT_TRUE(d3d12Layout->HasRootParameter(1));
+    EXPECT_TRUE(d3d12Layout->HasRootParameter(100));
+    EXPECT_TRUE(d3d12Layout->HasRootParameter(200));
+    EXPECT_NE(d3d12Layout->GetRootParameterIndex(0), d3d12Layout->GetRootParameterIndex(1));
+
+    layout->Shutdown();
+    delete layout;
+}