Uniform Buffer Array is not supported by PowerVR GE8300?

PowerVR Insider
1

I have the following vertex shader that has one uniform buffer array matArry[4] to host per-object model-view-matrix; a push constants data matIndex used to choose the matrix from the uniform buffer array.

layout (std140, set = 0, binding = 1) uniform modelViewMatrixBuf
{	
	mat4 modelViewMat;
} matArry[4];

layout(push_constant) uniform pushConstansBuf
{
	...
	uint matIndex;		//Matrix array index (4-bytes)
};

void main()
{
	...
	gl_Position  = pos3D * matArray[matIndex].modelViewMat * projMat;
	...
}

This solution works well on all pltforms (AMD, nVidia, Adreno, Mali) except PowerVR GE8300 with Vulkan driver 1.0. On GE8300, Vulkan renders nothing without any run-time errors. Once I change the uniform buffer array back to a single buffer, it renders correctly.
Is that because uniform buffer array is not supported by PowerVR GE8300?

2

Hi,

I think uniform buffers work fine for us. Have you tried double checking your results with Renderdoc?

bests,
Marton

3

Renderdoc does not work well with my Acer Iconia tablet, apps can be remotely launched but crashed right away, I tried numbers of different apps, including PowerVR samples, none of them can be captured by Renderdoc.

Seeing that I can not use renderdoc, I’d like to know if there is a sample project shows using uniform buffer array (preferrably from powerVR SDK), do you know which one demonstrate this?

4

Hi hongkun, could you share your simple test project with this problem ? did you test some examples from Sascha Willems ?

5

Sorry for late reply, I have been busy on other things lately.
I have given up using uniform buffer array at shader side, instead, I’m now using buffer/descriptor array at CPU side. The reason is that I also found few other platforms (like MoltenVK for macOS / iOS) give me headache when using uniform buffer array in the shader.

6

Hi…as a workaround if you replace the loop iteration with a literal constant rather than a uniform it seems to work correctly; while not ideal it’s a lot better than manual loop unrolling. We’ll try and come up with a better workaround for you.

7

Thanks for your suggestions!