new example: using compileManager to change between programs

[theodoregoetz]

The example utils/vsgcompilemanager switches between two scenes, one that uses a storage buffer and another that does not. This switch happens every 60 frames. On the third time showing the scene with the storage buffer, VSG emits the following warning:

Warning: Context::reserve(const ResourceRequirements& requirements) 
invalid combination of required_maxSets (0) & required_descriptorPoolSizes (1) 
unable to allocate DescriptorPool.

[robertosfield]

@theodoregoetz is this example still useful?

[theodoregoetz]

I just ran it with -d -v and now emits a new validation error:

VUID-RuntimeSpirv-NonWritable-06340(ERROR / SPEC): msgNum: 269944751 - Validation Error: [ VUID-RuntimeSpirv-NonWritable-06340 ] Object 0: handle = 0x5f000000005f, type = VK_OBJECT_TYPE_SHADER_MODULE; | MessageID = 0x101707af | vkCreateGraphicsPipelines(): pCreateInfos[0].pStages[1] SPIR-V (VK_SHADER_STAGE_FRAGMENT_BIT) uses descriptor [Set 0, Binding 0, variable "CellColors"] (type VK_DESCRIPTOR_TYPE_STORAGE_BUFFER_DYNAMIC or VK_DESCRIPTOR_TYPE_STORAGE_BUFFER) which is not marked with NonWritable, but fragmentStoresAndAtomics was not enabled. The Vulkan spec states: If fragmentStoresAndAtomics is not enabled, then all storage image, storage texel buffer, and storage buffer variables in the fragment stage must be decorated with the NonWritable decoration (https://www.khronos.org/registry/vulkan/specs/1.3-extensions/html/vkspec.html#VUID-RuntimeSpirv-NonWritable-06340)
    Objects: 1
        [0] 0x5f000000005f, type: 15, name: NULL

I think this can be fixed by adding "readonly" on the buffers in the shader code. But beyond that, it's still a valid test, if not exactly an example per-se. Do you have a better place for test programs?

[robertosfield]

We don't presently have test specific place, but perhaps we should have vsgExamples/tests directory alongside vsgExamples/examples?

[robertosfield]

I have merged the vsgcompilemanager test program into a branch and moved it into vsgExamples/tests. Running 'vsgcompilemanager -d' I see:

VUID-RuntimeSpirv-NonWritable-06340(ERROR / SPEC): msgNum: 269944751 - Validation Error: [ VUID-RuntimeSpirv-NonWritable-06340 ] Object 0: handle = 0x95a125000000001a, type = VK_OBJECT_TYPE_SHADER_MODULE; | MessageID = 0x101707af | vkCreateGraphicsPipelines(): pCreateInfos[0].pStages[1] SPIR-V (VK_SHADER_STAGE_FRAGMENT_BIT) uses descriptor [Set 0, Binding 0, variable "CellColors"] (type VK_DESCRIPTOR_TYPE_STORAGE_BUFFER or VK_DESCRIPTOR_TYPE_STORAGE_BUFFER_DYNAMIC) which is not marked with NonWritable, but fragmentStoresAndAtomics was not enabled. The Vulkan spec states: If fragmentStoresAndAtomics is not enabled, then all storage image, storage texel buffer, and storage buffer variables in the fragment stage must be decorated with the NonWritable decoration (https://vulkan.lunarg.com/doc/view/1.3.290.0/linux/1.3-extensions/vkspec.html#VUID-RuntimeSpirv-NonWritable-06340)
    Objects: 1
        [0] 0x95a125000000001a, type: 15, name: NULL
VUID-RuntimeSpirv-NonWritable-06340(ERROR / SPEC): msgNum: 269944751 - Validation Error: [ VUID-RuntimeSpirv-NonWritable-06340 ] Object 0: handle = 0x74ea280000000054, type = VK_OBJECT_TYPE_SHADER_MODULE; | MessageID = 0x101707af | vkCreateGraphicsPipelines(): pCreateInfos[0].pStages[1] SPIR-V (VK_SHADER_STAGE_FRAGMENT_BIT) uses descriptor [Set 0, Binding 0, variable "CellColors"] (type VK_DESCRIPTOR_TYPE_STORAGE_BUFFER or VK_DESCRIPTOR_TYPE_STORAGE_BUFFER_DYNAMIC) which is not marked with NonWritable, but fragmentStoresAndAtomics was not enabled. The Vulkan spec states: If fragmentStoresAndAtomics is not enabled, then all storage image, storage texel buffer, and storage buffer variables in the fragment stage must be decorated with the NonWritable decoration (https://vulkan.lunarg.com/doc/view/1.3.290.0/linux/1.3-extensions/vkspec.html#VUID-RuntimeSpirv-NonWritable-06340)
    Objects: 1
        [0] 0x74ea280000000054, type: 15, name: NULL

I have a look into the shaders it's using.

[robertosfield]

As you suspect, adding readonly fixed the validation error:

diff --git a/tests/vsgcompilemanager/vsgcompilemanager.cpp b/tests/vsgcompilemanager/vsgcompilemanager.cpp
index 4d8fc72f..7ff48a33 100644
--- a/tests/vsgcompilemanager/vsgcompilemanager.cpp
+++ b/tests/vsgcompilemanager/vsgcompilemanager.cpp
@@ -13,7 +13,7 @@ void main() { gl_Position = (projection * modelView) * vec4(vertex, 1.0); }
 
 std::string FRAG0{R"(
 #version 450
-layout(set = 0, binding = 0) buffer CellColors { vec4[] cellColors; };
+layout(set = 0, binding = 0) readonly buffer CellColors { vec4[] cellColors; };
 layout(location = 0) out vec4 color;
 void main() { color = cellColors[gl_PrimitiveID]; }
 )"};

[robertosfield]

I have now merged this test program with vsgExamples master.