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| void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
vec2 uv = ( fragCoord * 2.0 - iResolution.xy )/iResolution.y;
vec3 cameraPos = vec3(0.0, 0.0, 0.0);
vec3 targetPos = vec3(cos(iTime), 0.0, sin(iTime));
// camera space
vec3 yAxis = vec3(0.0, 1.0, 0.0);
vec3 zAxis = normalize(targetPos - cameraPos);
vec3 xAxis = normalize(cross(zAxis, yAxis));
float fov = 90.0;
float a = radians(fov/2.0);
// ==============================
// 1. cube
vec3 pos = normalize(uv.x * xAxis + uv.y * yAxis + 1.0/tan(a) * zAxis);
// 2. sphere
/*float z = sqrt(1.0 - uv.x*uv.x - uv.y*uv.y);
vec3 pos = normalize(uv.x * xAxis + uv.y * yAxis + z * zAxis); */
// ==============================
fragColor = vec4(texture(iChannel0, pos).xyz, 1.0);
}
|
1. cube
世界坐标为$（ uv, t = \frac{1.0}{tan(a)} ）$，camera space坐标系为$（xAxis, yAxis, zAxis ）$
坐标系转换world->camera:
1
| vec3 pos = normalize(uv.x*xAxis + uv.y*yAxis + 1.0/tan(a)*zAxis);
|
2. sphere
sphere半径为1，求出z，得到世界坐标，转换到camera space