Created
August 14, 2018 02:24
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shader_type canvas_item; | |
/** | |
Maps object texture onto a sphere and applies a spherical normal | |
based on a simulated light. | |
Adapted from | |
https://www.raywenderlich.com/2323-opengl-es-pixel-shaders-tutorial | |
and | |
https://gamedev.stackexchange.com/a/9385 | |
**/ | |
void fragment() { | |
float pi = 3.14159; | |
float x = (UV.x - 0.5) * 2.0; | |
float y = (UV.y - 0.5) * 2.0; | |
float r = sqrt(x * x + y * y); | |
float d = bool(r) ? asin(r)/r : 0.0; | |
float x2 = d * x; | |
float y2 = d * y; | |
float rot_speed = 16.0; // smaller values rotate faster | |
float x3 = mod(x2 / (4.0 * pi) + 0.5 + TIME / rot_speed, 1.0); | |
float y3 = y2 / (2.0 * pi) + 0.5; | |
//simulated light vector | |
vec3 cLight = normalize(vec3(-0.5, -0.5, 1.0)); | |
vec2 center = vec2(0.5, 0.5); | |
float radius = 0.5; | |
vec2 position = UV - center; | |
float z = sqrt(radius * radius - position.x * position.x - position.y * position.y); | |
vec3 normal = normalize(vec3(position.x, position.y, z)); | |
if (length(position) > radius) { //discard pixels outside the sphere | |
discard; | |
} else { | |
float diffuse = max(0.0, dot(normal, cLight)); | |
vec4 sample = texture(TEXTURE,vec2(x3,y3)); //grab sphere-mapped pixel from texture | |
COLOR = vec4(vec3(diffuse), 1.0) * sample; | |
} | |
} | |
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