CODEWITHSUNDEEP
openglshaderlibgdx
Luan Nico
Luan Nico

Reputation: 5927

Use only a Fragment Shader in libGDX?

I am porting my project from pure LWJGL to libGDX, and I'd like to know if there is a way to create a program only with the Fragment Shader?

What I'd like to do is to change the color of my texture where it is gray to a color I receive as a parameter. The shader worked perfectly before, but now, it seems that I need to add a Vertex Shader - what does not make any sense to me. So I wrote this:

void main() {
    gl_Position = ftransform();
}

That, according to the internet, is the simplest possible VS: it does nothing, and it really shouldn't. But it doesn't work: nothing is displayed, and no compilation errors or warnings are thrown. I tried to replace my Fragment Shader with a simpler one, but the results were even stranger:

void main() {
    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}

This should only paint everything in red. But when I run, the program crashes, no error is thrown, no Exception, very odd behavior. I know that libGDX adds tilting, but I don't think it would work either, because I need to replace only the gray-scale colors, and depending on the intensity, I need to correctly modulate the correct color (that is varying). Another shader I am using (Fragment only, again) is to set the entire scene to gray-scale (when on the pause menu). It won't work either.

Upvotes: 1

Views: 872

Answers (1)

datenwolf
datenwolf

Reputation: 162327

When it comes to shaders in modern OpenGL you always have to supply at least a vertex and a fragment shader. OpenGL-2 gave you some leeway, at the drawback, that you then still have to struggle with the arcane fixed function state machine.

That, according to the internet, is the simplest possible VS: it does nothing, and it really shouldn't.

What makes you think it does "nothing". Of course it does something: It translates incoming, raw numbers into something sensible, namely vertices in clip space.

Upvotes: 2

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