What is simplest way to flip uv coordinates?

[slapin]

Hi, all!
How can I flip UVs by Y when Vulkan is used and not flip
when OpenGL is used? Need to support both.

Ogre Version: master branch
Operating System: Ubuntu 22.04
Render System: GL ES 2.0, Vulkan

[rpgplayerrobin]

For my water I use reflection, and then I do need to flip the projection coords between OpenGL and Direct3D, maybe this will also help in your scenario?

I use this in the shader material:

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default_params
{
	param_named_auto renderTargetFlipping render_target_flipping
}

Then in the hlsl code I use this:

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float renderTargetFlipping;

float4 main_ps( float4 projectionCoord : TEXCOORD0 ) : COLOR0
{
	float2 projectionUV = projectionCoord.xy / projectionCoord.w;
	projectionUV.y = (1.0 - saturate(renderTargetFlipping)) + renderTargetFlipping * projectionUV.y;

Otherwise, you could simply add your own parameter and then just set it in code:

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param_named flipUVY float 1.0

You could also use a shared parameter for it, in the shader material:

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shared_params_ref FlipParams

In C++:

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GpuSharedParametersPtr tmpGpuSharedParameters = GpuProgramManager::getSingleton().createSharedParameters("FlipParams");
tmpGpuSharedParameters->addConstantDefinition("flipUVY", GCT_FLOAT);
if(IsUsingVulkan)
	tmpGpuSharedParameters->setNamedConstant("flipUVY", 1.0f);
else
	tmpGpuSharedParameters->setNamedConstant("flipUVY", -1.0f);

And then simply just add it normally in the shader itself:

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float flipUVY;

[slapin]

Thanks a lot!

[slapin]

looks like renderTargetFlipping works in reverse for me

[paroj]

whats wrong if #ifdef?
https://github.com/OGRECave/ogrewater/b ... P.glsl#L58

[slapin]

ifdef is good too, thanks!