#version 150

uniform mat4 transform;

uniform mat4 projection;

uniform mat4 modelview;

uniform vec4 viewport;

uniform int perspective;

in vec4 position;

in vec4 color;

out vec4 vertColor;

void main() {

gl_PointSize = 1.0;

//vec4 worldPosition = transform * position;

//gl_Position = worldPosition;

vec4 pos = modelview * position;

vec4 clip = projection * pos;

// Perspective ---

// convert from world to clip by multiplying with projection scaling factor

// invert Y, projections in Processing invert Y

vec2 perspScale = (projection * vec4(1, -1, 0, 0)).xy;

// No Perspective ---

// multiply by W (to cancel out division by W later in the pipeline) and

// convert from screen to clip (derived from clip to screen above)

vec2 noPerspScale = clip.w / (0.5 * viewport.zw);

gl_Position.xy = clip.xy + mix(noPerspScale, perspScale, float(perspective > 0));

gl_Position.zw = clip.zw;

vertColor = color;

}