Raymarching with depth writting

There’s a lot of raymarching shaders, but I found no one that writes the result depth to the depth buffer, so other meshes without any shader don’t clip properly with the raymarched geometry.
So I made a simple version with depth writting, so you can see that other meshes interacts with the raymarched geometry.
It only works in GLES3, as GLES2 don’t support depth writting.

Shader code
shader_type spatial;

// Raymarching constants
const float SURFACE_DST = .01;
const int MAX_STEPS = 64;
const float MAX_DISTANCE = 256f;
const float NORMAL_STEP = .001f;

varying float time;

void vertex() {
	time = TIME;
}

// Rotation matrix from angle
mat3 rotateY(float theta) {
    float c = cos(theta);
    float s = sin(theta);
    return mat3(
        vec3(c, 0, s),
        vec3(0, 1, 0),
        vec3(-s, 0, c)
    );
}

// Torus signed distance field function
float SDFTorus(vec3 p, float innerRadius, float radius) {
	vec2 q = vec2(length(p.xz) - radius, p.y);
	return length(q) - innerRadius;
}

// Sphere signed distance field function
float SDFSphere(vec3 p, float radius) {
	return length(p) - radius;
}

// Box signed distance field function
float SDFBox(vec3 p, vec3 size) {
	vec3 d = abs(p) - size;
	return min(max(d.x,max(d.y,d.z)),0.0) + length(max(d,0.0));
}

// Sample the whole scene, you can mix multiple shapes here
float Scene(vec3 pos) {
	// Torus
	float dst = SDFTorus(pos, .5f, 2f);
	
	// Rotating spheres
	vec3 spOff1 = vec3(cos(time * 3.1415), 0f, sin(time * 3.1415)) * 2f;
	vec3 spOff2 = vec3(cos((time + 1f) * 3.1415), 0f, sin((time + 1f) * 3.1415)) * 2f;
	dst = min(dst, SDFSphere(pos + spOff1, 1f));
	dst = min(dst, SDFSphere(pos + spOff2, 1f));
	
	// Warping box
	vec3 boxPos = pos;
	boxPos.z += cos(boxPos.y * 3.1415 * .5f) * .5f - 1f;
	boxPos = rotateY(boxPos.y * 3.1415 * .2f) * boxPos;
	dst = min(dst, SDFBox(boxPos, vec3(1f, 4f, 1f)));
	
	return dst;
}

// The actual raymarching function
float RayMarch(vec3 ro, vec3 rd) {
	float d = 0f;
	for (int i = 0; i < MAX_STEPS; i++) {
		vec3 pos = ro + rd * d;
		float sceneDst = Scene(pos);
		
		d += sceneDst;
		
		// Only stop if distance is higher than MAX_DISTANCE or sampled distance
		// is less that surface threshold
		if (d > MAX_DISTANCE || abs(sceneDst) <= SURFACE_DST) break;
	}
	return d;
}

// Sample the world normal in the contact position
vec3 Normal(vec3 pos) {
	float d = Scene(pos);
	vec2 e = vec2(NORMAL_STEP, 0.0);
	vec3 n = d - vec3(
		Scene(pos - e.xyy),
		Scene(pos - e.yxy),
		Scene(pos - e.yyx));
	return normalize(n);
}

void fragment() {
	// Get the pixel world coordinates
	vec3 world = (CAMERA_MATRIX * vec4(VERTEX, 1.0)).xyz;
	// Get the camera position
	vec3 camera = (CAMERA_MATRIX * vec4(0.0, 0.0, 0.0, 1.0)).xyz;
	// Raymarching direction
	vec3 dir = normalize(world - camera);
	
	// Starts just a bit off the mesh surface
	vec3 ro = world - dir * SURFACE_DST;
	vec3 rd = dir;
	
	// Raymarch
	float d = RayMarch(ro, rd);
	// Set the world position from the raymarching output
	world = ro + rd * d;
	
	if (d >= MAX_DISTANCE) discard;
	
	// Samples world normal
	vec3 n = Normal(world);
	// Set the local normal relative to the view
	NORMAL = (INV_CAMERA_MATRIX * vec4(n, 0f)).xyz;
	
	// Depth calculation, this makes possible for other meshes intersect
	// properly with the geometry
	vec4 ndc = PROJECTION_MATRIX * INV_CAMERA_MATRIX * vec4(world, 1f);
	float depth = (ndc.z / ndc.w) * .5f + .5f;
	DEPTH = depth;
}
Tags
depth, raymarch
The shader code and all code snippets in this post are under CC0 license and can be used freely without the author's permission. Images and videos, and assets depicted in those, do not fall under this license. For more info, see our License terms.

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