World position and Object position in Shader Fragment

October 19, 2016

World position and Object position in Shader Fragment

When you write a Shader Fragment, you should use the right naming conventions. For example if you check parameters like “mayaUvCoordSemantic” the name should be “uvCoord”, for “tangent” the name should be “mayaTangentIn”.

Even if you check the “Object Space Position” the name and the semantic both should be “Pm”. Check the below example.

<fragment uiName=\"depthShaderPluginInterpolantFragment\" name=\"depthShaderPluginInterpolantFragment\" type=\"interpolant\" class=\"ShadeFragment\" version=\"1.0\">"
<description><![CDATA[Depth shader vertex fragment]]></description>"
<properties>
<float3 name=\"Pm\" semantic=\"Pm\" flags=\"varyingInputParam\" />
<float4x4 name=\"worldViewProj\" semantic=\"worldviewprojection\" />
</properties>
<vertex_source><![CDATA["
float idepthShaderPluginInterpolantFragment(float3 Pm, float4x4 worldViewProj)
{
float4 pCamera = mul(worldViewProj, float4(Pm, 1.0f));
return (pCamera.z - pCamera.w*2.0f); \n"
} ]]>
</vertex_source>

If you are defining, "World Space Position" the semantic and the name should be “Pw” instead of any other string like “out”, "outPosition",... like below. If you use any other string, Maya won't consider it as varyingInputParameters.

<float3 name=\"Pw\” semantic=\"Pw\” flags=\"varyingInputParam\" />"
...
<![CDATA[float4 fragTexture(float2 uv, texture2D map, sampler2D textureSampler, float4x4 texMatrix, float3 Pw)
...

Semantic	Name	Type	Meaning
Pm	Pm	3-float	Object space position
Pw	Pw	3-float	World space position
Pv	Pv	3-float	View space position
Nm	Nm	3-float	Object space normal
Nw	Nw	3-float	World space normal