3D [GMS 1.4] Get surface depth buffer

[DigitalRealms]

Hello guys. I am trying to implement some shadow mapping in my game using GMS 1.4.
To optimize things i need to disable fragment shader and sample depth buffer only (as a texture).
So,
1. Can i get surface's depth buffer somehow?
2. Can i disable fragment shader (but it is not so important, because i can just create a dummy fragment shader)

Thanks.

 

[sp202]

No to both.

 

[TheSnidr]

You'll need to make your own depth buffer

 

[rytan451]

Here's a quick shader I whipped up to write a depth buffer.

// Vertex shader
attribute vec3 in_Position;
void main() {
	gl_Position = gm_Matrices[MATRIX_WORLD_VIEW_PROJECTION] * vec4(in_Position, 1.);
}

// Fragment shader
void main() {
	gl_FragColor = fract(vec4(gl_FragCoord.z) * vec4(1., 256., 65536., 16777216.));
}

// Compare operator (returns true if lval > rval)
bool zbuffGreaterThan(vec4 lval, vec4 rval) {
	return (lval.x > rval.x) || (lval.x == rval.x && lval.y > rval.y) || (lval.xy == rval.xy && lval.z > rval.z) || (lval.xyz == rval.xyz && lval.w > rval.w);
}

 

[sp202]

@rytan451 That's not necessary, surfaces do have working depth buffers, they just can't be read from, hence depth has to be encoded using colour instead.

 

[DigitalRealms]

You'll need to make your own depth buffer

Thats what i need i guess. But how??)

 

[Binsk]

Thats what i need i guess. But how??)

In GM it is a bit more complicated. You need to do either an extra pass to render the depth to a surface as your buffer (via custom fragment shader) or use MRTs to render your depth alongside your regular render.

GameMaker only has RGBA8 surfaces, however, so for precision you have to split your 32bit or 24bit depth data into separate 8 bit chanels when writing and re-combine when reading. All this happens in your fragment shader.

 

[rytan451]

@rytan451 That's not necessary, surfaces do have working depth buffers, they just can't be read from, hence depth has to be encoded using colour instead.

Yes, and that's what the shader is for: to encode depth using colour.

 

[sp202]

Yes, and that's what the shader is for: to encode depth using colour.

Yep, sorry, just meant that the depth comparison was unnecessary, the part about the colour was moreso directed at OP but I phrased it badly.