2 KiB
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.