Drawing functions for GLSL in GLSL Sandbox

draw.glsl

#ifdef GL_ES
precision mediump float;
#endif

uniform float time;
uniform vec2 mouse;
uniform vec2 resolution;

//draw.glsl: Drawing functions for GLSL

#define SET_COLOR4(COLOR) gl_FragColor = COLOR
#define SET_COLOR3(COLOR) gl_FragColor = vec4(COLOR, 1.0)

#define EQUALS(X, Y) (X > Y-0.001 && X < Y+0.001)

#define BLEND(A, B) mix(A, B, A.a*B.a)

float aspect;
vec2 uvUnit;
vec2 position;
mat4 projection;

void draw_point(vec2 pposition, vec4 color) {
	if (EQUALS(pposition.x, position.x) && EQUALS(pposition.y, position.y)) {
		SET_COLOR3(BLEND(gl_FragColor, color).xyz);
	}
}

void draw_circle(vec2 cposition, float radius, vec4 color) {
	vec2 np = pow(position-cposition, vec2(2.0));
	float dist = sqrt(np.x+np.y);
	
	if (dist < radius) {
		SET_COLOR3(BLEND(gl_FragColor, color).xyz);
	}
}

void draw_rectangle(vec2 rposition, vec2 size, vec4 color) {
	if (position.x > rposition.x && position.y > rposition.y && position.x < rposition.x+size.x && position.y < rposition.y+size.y) {
		SET_COLOR3(BLEND(gl_FragColor, color).xyz);
	}
}

void draw_triangle(vec2 a, vec2 b, vec2 c, vec4 color) {
	vec2 v0 = c-a;
	vec2 v1 = b-a;
	vec2 v2 = position-a;
	
	float dot00 = dot(v0, v0);
	float dot01 = dot(v0, v1);
	float dot02 = dot(v0, v2);
	float dot11 = dot(v1, v1);
	float dot12 = dot(v1, v2);
	
	float invDenom = 1.0 / (dot00*dot11-dot01*dot01);
	float u = (dot11 * dot02 - dot01 * dot12) * invDenom;
	float v = (dot00 * dot12 - dot01 * dot02) * invDenom;
	
	if (u >= 0.0 && v >= 0.0 && u+v < 1.0) {
		SET_COLOR3(BLEND(gl_FragColor, color).xyz);
	}
}

mat4 guPerspective(float fovy,float aspect,float n,float f) {
	float cot,angle,tmp;
	
	mat4 mt;

	angle = fovy*0.5;
	angle = radians(angle);
	
	cot = 1.0/tan(angle);

	mt[0][0] = cot/aspect;
	mt[0][1] = 0.0;
	mt[0][2] = 0.0;
	mt[0][3] = 0.0;

	mt[1][0] = 0.0;
	mt[1][1] = cot;
	mt[1][2] = 0.0;
	mt[1][3] = 0.0;
	
	tmp = 1.0/(f-n);
	mt[2][0] = 0.0;
	mt[2][1] = 0.0;
	mt[2][2] = -(n)*tmp;
	mt[2][3] = -(f*n)*tmp;
	
	mt[3][0] = 0.0;
	mt[3][1] = 0.0;
	mt[3][2] = -1.0;
	mt[3][3] = 0.0;
	
	return mt;
}

mat4 makeRotationX(float theta) {
	float c = cos(theta);
	float s = sin(theta);
	return mat4(1, 0,  0, 0,
			0, c, - s, 0,
			0, s,  c, 0,
			0, 0,  0, 1);
}

mat4 makeRotationY(float theta) {
	float c = cos(theta);
	float s = sin(theta);
	return mat4(c, 0, s, 0,
			 0, 1, 0, 0,
			- s, 0, c, 0,
			 0, 0, 0, 1);
}

mat4 makeRotationZ(float theta) {
	float c = cos(theta);
	float s = sin(theta);
	return mat4(c, - s, 0, 0,
			s,  c, 0, 0,
			0,  0, 1, 0,
			0,  0, 0, 1);
}

mat4 makeTranslation(float x, float y, float z) {
	return mat4(1, 0, 0, x,
			0, 1, 0, y,
			0, 0, 1, z,
			0, 0, 0, 1);
}

void draw_triangle3d(vec3 a, vec3 b, vec3 c, vec4 color) {
	draw_triangle((projection*vec4(a,1.0)).xy, (projection*vec4(b,1.0)).xy, (projection*vec4(c,1.0)).xy, color);
}

#define X 0.25
#define Y -0.25
#define CLR vec4(1.0,1.0,1.0,position.x)

void main( void ) {
	aspect = resolution.x/resolution.y;
	uvUnit = 1.0 / resolution.xy;
	vec2 uv = ( gl_FragCoord.xy / resolution.xy );
	position = (uv-0.5);
	position.x *= aspect;
	position += 0.5;
	
	projection = guPerspective(75.0, aspect, 0.0, 10.0)*makeRotationX(time)*makeRotationY(time)*makeRotationZ(time);
	
	gl_FragColor = vec4( position, 0.0, 1.0 );
	
	position -= 0.5;
	
	/*draw_point(vec2(0.5, 0.5), vec4(vec3(1.0),0.5));
	
	draw_circle(vec2(0.5, 0.5), 0.2, vec4(vec3(1.0),0.5));
	
	draw_rectangle(vec2(0.25,0.25),vec2(0.5),vec4(vec3(1.0),0.5));
	
	draw_triangle(vec2(0.25,0.25), vec2(0.75,0.25), vec2(0.5, 0.75), vec4(vec3(1.0),0.5));*/
	
	//front
	draw_triangle3d(vec3(Y,Y,Y),vec3(Y,X,Y),vec3(X,X,Y),CLR);
	draw_triangle3d(vec3(X,X,Y),vec3(X,Y,Y),vec3(Y,Y,Y),CLR);
	
	//bottom
	draw_triangle3d(vec3(Y,Y,Y),vec3(Y,Y,X),vec3(X,Y,X),CLR);
	draw_triangle3d(vec3(X,Y,X),vec3(X,Y,Y),vec3(Y,Y,Y),CLR);
	
	//back
	draw_triangle3d(vec3(Y,Y,X),vec3(Y,X,X),vec3(X,X,X),CLR);
	draw_triangle3d(vec3(X,X,X),vec3(X,Y,X),vec3(Y,Y,X),CLR);
	
	//top
	draw_triangle3d(vec3(Y,X,Y),vec3(Y,X,X),vec3(X,X,X),CLR);
	draw_triangle3d(vec3(X,X,X),vec3(X,X,Y),vec3(Y,X,Y),CLR);
	
	//left
	draw_triangle3d(vec3(Y,Y,Y),vec3(Y,Y,X),vec3(Y,X,X),CLR);
	draw_triangle3d(vec3(Y,X,X),vec3(Y,X,Y),vec3(Y,Y,Y),CLR);
	
	//right
	draw_triangle3d(vec3(X,Y,Y),vec3(X,Y,X),vec3(X,X,X),CLR);
	draw_triangle3d(vec3(X,X,X),vec3(X,X,Y),vec3(X,Y,Y),CLR);
}