surface_shader reading specific values causes wrong color

OnkelDagobert · January 2013

Hi,
I'm having Problems writing the shader for a material.

<shader>	
	<inputs>		
	</inputs>
	<params>
		<param name="osPosition">true</param>
		<param name="wsPosition">true</param>
		<param name="wsNormal">true</param>
		<param name="vsNormal">true</param>
		<param name="twoSided">true</param>
		<param name="alphaTest">true</param>
	</params>
	<code>
	<![CDATA[				
		void MaterialShader(in Material_Input input, inout Material material)
		{				
			material.emissive   =    float3(0,0,1);
		}
	]]>		
	</code>
</shader>

this shader works fine and gives me this (the blue glass):

but if i try to read some vars it give me a total wrong result:

<shader>	
	<inputs>		
	</inputs>
	<params>
		<param name="osPosition">true</param>
		<param name="wsPosition">true</param>
		<param name="wsNormal">true</param>
		<param name="vsNormal">true</param>
		<param name="twoSided">true</param>
		<param name="alphaTest">true</param>
	</params>
	<code>
	<![CDATA[				
		void MaterialShader(in Material_Input input, inout Material material)
		{						
			float3 neverused = viewPoint.xyz ;			
			material.emissive   =    float3(0,0,1);
		}
	]]>		
	</code>
</shader>

the material color ALLWAYS becomes purple, no matter what i write into material.emissive

this happens if i try to read following vars:
- viewPoint
- worldToScreenMatrix
- worldToCameraMatrix
and maybe some more

even though it makes the Color purple it reads the right values from this varibales

does anyone know what to do?

or is there a way get the distance from the cam to the displaying object without using viewPoint?

Ineluki80 · January 2013

I'm fairly new to shaders and all (only wrote a pixel shader so far), so I wonder: where do you take viewPoint from ?
I can not see where this variable is defined nor is it an intrinsic HLSL function.
So maybe you are accessing an undefinded variable, causing a shader compile error and as a result get some default or uninitialized material instead ?
Have you had a look at the debug output messages withing the console ?

OnkelDagobert · January 2013

it is defined in core\renderer\Deferred.shader_template

and as i said the value in viewPoint is correct. I tested it by adding a glow to the material depending on the viewPoint

OnkelDagobert · February 2013

ok got it..
it seems that the purple color is the right behavior.
the shader used the default values specified in Deferred.shader_template:

// Setup default values so that the shader can only set the values it wants to.
material.albedo   			= float3(1, 0, 1);
material.tsNormal 			= float3(0, 0, 1);
material.opacity  			= 1;
material.specular 			= float3(0, 0, 0);
material.gloss    			= 0;
material.emissive 			= float3(0, 0, 0);
material.wsOffset 			= float3(0, 0, 0);
material.infestationShell 	= 0;	// Hack to make the infestation shell pass run
material.scale 				= 1;
material.ssDistortion 		= float2(0, 0);
material.transmissionColor 	= float3(1, 1, 1);

so a

material.albedo  = float3(0, 0,0);

fixed it

but why does the shader sometimes use these default values and sometimes not?

surface_shader reading specific values causes wrong color

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