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AppGameKit Classic Chat / Basic 2D shader questions: co-ordinates

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nz0
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Posted: 5th Aug 2017 00:00
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I want to be able to work with co-ords rather than percentage in the sprite frag shader.

I ultimately need to pass multiple x,y co-ords to my shader, but first I have to work out what a screen pixel is.

I could do 1.0/1024.0 or that kind of thing, but is there a way to use a passed var like AGK_Ortho to quickly reference pixels?

I should say that I am using a full screen sprite, so it will always be the same size as "resolution".

In the same question, how does SetShaderConstantArrayByName( shaderID, szName, arrayIndex, value1, value2, value3, value4 ) work? Can I use it on 2D shaders?
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Markus
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Posted: 5th Aug 2017 08:41 Edited at: 5th Aug 2017 08:43
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maybe this helps
GetSpritePixelFromX ( iSpriteIndex, x )
GetSpritePixelFromY ( iSpriteIndex, y )
that coords belongs the used image position.
i guess you are looking for the back buffer size.

from reading the agk docu i would say yes you can. it seems it fills a vec4 type.
https://www.khronos.org/opengl/wiki/Uniform_(GLSL)
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janbo
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Posted: 5th Aug 2017 14:23
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I think 1.0/agk_resolution should do the trick.
from the agk doc: vec2 agk_resolution - The resolution of the current render target, image or window
Quote: "use a passed var like AGK_Ortho"

I'm not sure what you mean by that.
Quote: "how does SetShaderConstantArrayByName( shaderID, szName, arrayIndex, value1, value2, value3, value4 ) work ?"

It can pass float,vec2,vec3 and vec4...just start at value1

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nz0
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Posted: 7th Aug 2017 14:54
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How should I define the array in the shader?

Does it need to be pre-declared?
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janbo
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Posted: 7th Aug 2017 19:51
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Quote: "Does it need to be pre-declared?"

Yes

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