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render3d(vulkan): the ground reads the sun cascades itself - no separate terrain sun pass

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tersun.frag rasterised every terrain patch a second time into a screen buffer, because on OpenGL the
cascade read inside terrain.frag fell off a driver cliff (about 6 ms a frame). Vulkan has no such
cliff: its terrain programs are the SUN_INLINE variant, which evaluates the same two tiers with the
same normal and cross-fade in the ground's own shader, and terrain_draw skips the pass - in the frame
and in the water reflection. OpenGL keeps the pass. R3D_SUN_PASS=1 keeps it on Vulkan, for comparing.

Mac Vulkan town 1759 -> 1692 draws; frames within 2/255 of the pass (15331 px, float rounding). PC camp
1984 -> 1882 draws, 3.9 s for 400 frames either way, self-tests 59/59, validation 0. OpenGL frames
byte-identical.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
Orkun ÇAKILKAYA 2026-09-15 17:26:39 +03:00
parent eb1cd3e01a
commit 44ecd55a86
10 changed files with 240 additions and 5 deletions
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20
packages/ludic.render3d/shaders/terrain.frag
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@ -200,6 +200,20 @@ void triC(bool cheap, sampler2D d, sampler2D nm, sampler2D am, vec3 p, vec3 dpx,
if (cheap) { samplePlain(d, nm, am, p.xz * scale, dpx.xz * scale, dpy.xz * scale, alb, nrm, arm); nrm = normalize(vec3(nrm.x, 1.0, nrm.y) + vec3(0.0, 1e-3, 0.0)); }
else sampleTri(d, nm, am, p, dpx, dpy, n, scale, alb, nrm, arm);
}
#ifdef SUN_INLINE
// Vulkan: the cascades are read here, in the ground's own shader, and tersun.frag's pass - a second
// rasterisation of every patch - is not drawn. The cliff tersun.frag describes is OpenGL's driver, and
// OpenGL keeps that pass. The same normal, the same two tiers and the same cross-fade as tersun.frag.
uniform float u_far_split;
uniform float u_far_band;
float sunInline(vec3 p, float dist, float viewDepth) {
vec3 Ng = normalize(texture(u_height, v_huv).gba);
if (dist > u_far_split + u_far_band) return sunShadowCheap(p, Ng, viewDepth);
if (dist < u_far_split - u_far_band) return sunShadow(p, Ng, viewDepth);
return mix(sunShadow(p, Ng, viewDepth), sunShadowCheap(p, Ng, viewDepth),
smoothstep(u_far_split - u_far_band, u_far_split + u_far_band, dist));
}
#endif
vec3 groundShade(vec3 p, vec3 N, float slope, float dist, float viewDepth, bool cheap) {
// ---- material weights ----
float macro = fbmC(cheap, p.xz * 0.02, 2);
@ -411,9 +425,11 @@ vec3 groundShade(vec3 p, vec3 N, float slope, float dist, float viewDepth, bool
// ground's own relief is in the baked height-field shadow that sunShadow() applies
#ifdef TFAST_1
float shadow = 1.0;
#elif defined(SUN_INLINE)
float shadow = sunInline(p, dist, viewDepth);
#else
// tersun.frag computed this for exactly this pixel; see the note there for why the
// cascade read cannot happen in here.
// cascade read cannot happen in here (on OpenGL).
float shadow = texelFetch(u_sunshadow, ivec2(gl_FragCoord.xy), 0).r;
#endif
vec3 col = shade(p, n, alb, rough, metal, ao, shadow, viewDepth);
@ -421,8 +437,10 @@ vec3 groundShade(vec3 p, vec3 N, float slope, float dist, float viewDepth, bool
return col;
}
#ifndef SUN_INLINE
uniform float u_far_split;
uniform float u_far_band;
#endif
void main() {
vec3 p = v_wpos;
if (p.y < u_clip_y) discard;