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Re: [Public WebGL] Shader validator issue.



Oooohhhh...ikky!

So I can't control the LOD of a texture lookup in the frag shader?...Urgh!
 That's a pain in the butt!  There is a significant class of shader
algorithms related to image atlassing that kinda rely on that function.  I
may have to go talk to Microsoft about getting "WebD3D" working! :-)

Oh well, it's a really good thing that the validator works.  I guess I owe
someone my humblest apologies...again!

   -- Steve

> From a bit further up on page 77..
>
>> The built-ins suffixed with "Lod" are allowed only in a vertex
>> shader.
>
> That sounds like the problem :-)
>
>     - Vlad
>
> ----- Original Message -----
>> I think I may have found a validator bug.
>>
>> This shader is boiled down to the bare essentials from a much bigger
>> example...
>>
>> #ifdef GL_ES
>> precision highp float;
>> #endif
>>
>> uniform sampler2D diffuseMap ;
>>
>> void main()
>> {
>> gl_FragColor = texture2DLod ( diffuseMap, vec2(0.5,0.5), 0.0 ) ;
>> }
>>
>> It compiles and runs just fine under last nights' Firefox/Minefield in
>> both Linux & Windows with the validator disabled - but fails with this
>> error with the validator turned on:
>>
>> Error compiling shader:
>> ERROR: 0:10: 'texture2DLod' : no matching overloaded function found
>> ERROR: 0:10: 'assign' : cannot convert from 'const mediump float'
>> to 'FragColor mediump 4-component vector of float'
>> ERROR: 2 compilation errors. No code generated.
>> GL Error: 1281 in loadShaderPairFromString
>>
>> (It also fails in more sane cases, like when the second parameter is a
>> simple varying texCoord and when the third parameter is a float
>> variable).
>>
>> Is there a problem with texture2DLod? I think I'm using it correctly
>> per
>> page 77 of
>> http://www.khronos.org/registry/gles/specs/2.0/GLSL_ES_Specification_1.0.17.pdf
>>
>> It says:
>>
>> vec4 texture2DLod (sampler2D sampler, vec2 coord, float lod)
>>
>> Eh?
>>
>> -- Steve
>>
>>
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