GameMaker Open Graphics Library Shading layer_shader Example

MotionBlurLayerShader.MD

Simple fragment shader that creates a motion blur to the right to anything that is on the specified depth layer.

other.gml

//I had this in the RoomCreationCode
global.posXBlur = 0.5;
background_layer_id = layer_get_id("Background");
if !layer_get_shader(background_layer_id)
{
	layer_shader(background_layer_id, sh_motion_blur);	
	layer_script_begin(background_layer_id, shader_blur_start);
	layer_script_end(background_layer_id, shader_blur_end);
}

//This was a script named shader_blur_start
function shader_blur_start(){
	blur_shader = sh_motion_blur;
	u_blur = shader_get_uniform(blur_shader,"pos")
	shader_set_uniform_f(u_blur,global.posXBlur,0.5);
}

//This was a script named shader_blur_end
function shader_blur_end(){
	shader_reset();
}

sh_motion_blur.fsh

varying vec2 v_vTexcoord;
varying vec4 v_vColour;

uniform vec4 uvs;//left,top,width,height
uniform vec2 pos;//x,y

const int Quality = 2;

void main()
{
    //Normalize coordinates to the 0-1 range.
    vec2 Norm = (v_vTexcoord-uvs.xy)/uvs.zw;
    vec4 Color = vec4(0);
    for( float i=0.0;i<1.0;i+=1.0/float(Quality))
    {
        //Add the blur sample offset.
        vec2 Coord = Norm+(0.5-pos)*i;
        //Skip samples that are outside of this sprite!
        if ((abs(Coord.x-0.5)>.5) || (abs(Coord.y-0.5)>.5)) continue;
        //De-normalize the texture coordinates.
        Coord = Coord*uvs.zw+uvs.xy;
        Color += texture2D( gm_BaseTexture, Coord);
    }
    Color /= float(Quality);
    gl_FragColor =  Color *  v_vColour;
}

sh_motion_blur.vsh

//
// Simple passthrough vertex shader
//
attribute vec3 in_Position;                  // (x,y,z)
//attribute vec3 in_Normal;                  // (x,y,z)     unused in this shader.
attribute vec4 in_Colour;                    // (r,g,b,a)
attribute vec2 in_TextureCoord;              // (u,v)

varying vec2 v_vTexcoord;
varying vec4 v_vColour;

void main()
{
    vec4 object_space_pos = vec4( in_Position.x, in_Position.y, in_Position.z, 1.0);
    gl_Position = gm_Matrices[MATRIX_WORLD_VIEW_PROJECTION] * object_space_pos;
    
    v_vColour = in_Colour;
    v_vTexcoord = in_TextureCoord;
}