Materials: Shaders

Shaders are referring to GPU-oriented pieces of a program, performing shading and rendering related functions instead of letting the engine handle it.

In FTEQW you can specify a custom GLSL or HLSL shader using the program command inside a Material.

Example Shader

This is a primitive shader file. It includes the vertex and fragment program.

It will respond to the diffusemap only, which is loaded into the d_f variable. It can be modified from that point onwards. The commented out line will turn all of the output red.

Give it a try, or something!

//======= Copyright (c) 2015-2020 Vera Visions LLC. All rights reserved. =======
//
// Purpose: 
//
// Example surface
//==============================================================================

!!ver 110
!!samps diffuse

#include "sys/defs.h"

varying vec2 tex_c;

#ifdef VERTEX_SHADER
void main ()
{
	tex_c = v_texcoord; /* get our texture coordinates, which we'll use for the texture2D command */
	gl_Position = ftetransform(); /* place vertex into the place FTE wants us to put them at */
}
#endif

#ifdef FRAGMENT_SHADER
void main ()
{
	vec4 d_f = texture2D(s_diffuse, tex_c); /* load the fragment from our diffusemap sample */
	// d_f.rgb = vec3(1.0, 0.0, 0.0); /* turns out fragment (aka pixel) red */
	gl_FragColor = d_f; /* final pixel output is that of d_f */
}
#endif

Dissecting GLSL shaders

When we pass program <shadername> in our Material, the engine will load glsl/<shadername>.glsl to handle the material for us.

The shader in question needs to define a main function for both a vertex and a fragment shader. That's what the ifdefs are for in the above example.

You can not have separate files handle vertex/fragment programs, unlike in id Tech 4/Doom III.

At some point in the main function, we do have to set gl_Position and gl_FragColor respectively. Those can not be undefined.

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Materials: Shaders

Example Shader

Dissecting GLSL shaders

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