英文:
Raymarching Clamping coordinate makes weird streched artifacts
问题
I am trying to render a grid of spheres using ray marching. The SDF function looks like:
float sq_layer(vec3 p, vec3 bounding_box_min, vec3 bounding_box_max)
{
float cell_size = 4.0 / 16.0;
vec3 p0 = clamp(p.xyz, bounding_box_min, bounding_box_max);
p0 = mod(p0, cell_size) - cell_size * 0.5f;
float d_pt = sphereSDF(vec3(p0.x, p0.y, p0.z), 0.05f);
return d_pt;
}
But I am getting something like this:
For some more relevance, I tried changing the code up a bit:
float sq_layer(vec3 p, vec3 bounding_box_min, vec3 bounding_box_max)
{
vec3 cell_size = (bounding_box_max - bounding_box_min) / 4.0;
vec3 p0 = clamp(p.xyz, bounding_box_min, bounding_box_max);
p0 = mod(p0, cell_size) - cell_size * 0.5f;
float d_pt = boxSDF(p0, cell_size * 0.35);
return d_pt;
}
Still I get,
英文:
I am trying to render a grid of spheres using ray marching. The SDF function looks like:
float sq_layer(vec3 p, vec3 bounding_box_min, vec3 bounding_box_max)
{
float cell_size = 4.0 / 16.0;
vec3 p0 = clamp(p.xyz, bounding_box_min, bounding_box_max);
p0 = mod(p0, cell_size) - cell_size * 0.5f;
float d_pt = sphereSDF(vec3(p0.x, p0.y, p0.z), 0.05f)
return d_pt;
}
But I am getting something like this:
For some more relevance, I tried changing the code up a bit:
float sq_layer(vec3 p, vec3 bounding_box_min, vec3 bounding_box_max)
{
vec3 cell_size = (bounding_box_max - bounding_box_min) / 4.0;
vec3 p0 = clamp(p.xyz, bounding_box_min, bounding_box_max);
p0 = mod(p0, cell_size) - cell_size * 0.5f;
float d_pt = boxSDF(p0, cell_size * 0.35);
return d_pt;
}
Still I get,
答案1
得分: 5
使用您目前的坐标截断方式导致您的 SDF 返回一个接近表面的常数距离，因此您迭代次数用尽，导致看到的伪影。
与其截断，不如与边界框大小相同的盒形 SDF 进行交集：
float sq_layer(vec3 p, vec3 bounding_box_min, vec3 bounding_box_max)
{
float cell_size = 4.0 / 16.0;
vec3 p0 = mod(p, cell_size) - cell_size * 0.5f;
float d_pt = sphereSDF(p0, 0.05f);
// 以下是一个简化的盒形 SDF
vec3 bb_extents = (bounding_box_max - bounding_box_min) * .5;
vec3 bb_center = bounding_box_min + bb_extents;
vec3 bb_p = max(abs(p-bb_center)-bb_extents,0.);
float d_bb = max(max(bb_p.x,bb_p.y),bb_p.z);
// 与边界框相交的“球场”
return max(d_pt,d_bb);
}
英文:
Clamping the coordinates the way you do results in your sdf returning a constant distance very close to the surface, hence you're running out of iterations resulting in the artifacts you see.
Instead of clamping you want to do an intersection with a box sdf the size of your bounding box:
float sq_layer(vec3 p, vec3 bounding_box_min, vec3 bounding_box_max)
{
float cell_size = 4.0 / 16.0;
vec3 p0 = mod(p, cell_size) - cell_size * 0.5f;
float d_pt = sphereSDF(p0, 0.05f);
// the following is just a simplified box sdf
vec3 bb_extents = (bounding_box_max - bounding_box_min) * .5;
vec3 bb_center = bounding_box_min + bb_extents;
vec3 bb_p = max(abs(p-bb_center)-bb_extents,0.);
float d_bb = max(max(bb_p.x,bb_p.y),bb_p.z);
// intersect "sphere-field" with bounding box
return max(d_pt,d_bb);
}
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