CODEWITHSUNDEEP
openglglslshaderdistance
alawiii521
alawiii521

Reputation: 11

Distance between a given world coordinate(uniform) and the current pixel being rendered in GLSL?

I'am trying to make alpha larger the farther the pixel is from the lightsource.

How can I calculate the distance between my lightsource(u_lightSourcePosition) and the pixel being rendered?

I tried doing this:

float distance_from_point_to_pixel = distance(gl_FragCoord,v_lightSourcePosition)

but it didn't work.

Vertex shader

attribute vec3 a_position;
attribute vec4 a_color;
attribute vec2 a_texCoord0;

varying vec4 v_color;
varying vec2 v_texCoord0;
varying vec2 v_lightSourcePosition;


uniform mat4 u_projTrans;
uniform vec2 u_lightSourcePosition;

void main() {
    vec4 position = u_projTrans * vec4(a_position, 1.0);
    gl_Position = position;
    v_color = a_color;
    v_texCoord0 = a_texCoord0;
    v_lightSourcePosition = u_lightSourcePosition ;

}

Fragment shader

varying vec4 v_color;
varying vec2 v_texCoord0;

varying vec2 v_lightSourcePosition;

uniform sampler2D u_sampler2D;


void main() {
    vec4 color = texture2D(u_sampler2D, v_texCoord0) * v_color;
    float lightRadius = 400.0;
    float distance_from_point_to_pixel = distance(gl_FragCoord,v_lightSourcePosition);
    color.a = distance_from_point_to_pixel / lightRadius;
    gl_FragColor = color;
}

Upvotes: 0

Views: 1465

Answers (1)

Gabriel Reiser
Gabriel Reiser

Reputation: 402

You need the world space of the fragment. Pass it from the vertex shader to the pixel shader as another vec3 and you'll probably want to pass in a world/model matrix to translate a_position from object space to world space. vec3 pworld = (model * vec4(a_position,1.0)).xyz;

Upvotes: 1

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