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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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18
packages/ludic.render3d/terrain.ludic
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@ -32,6 +32,7 @@ var ter_prog: int = 0
var ter_prog_far: int = 0
var ter_prog_near: int = 0 # the detailed tier alone (NEAR_ONLY)
var ter_sun_prog: int = 0 # tersun.frag: sun visibility into a screen buffer
var ter_sun_inline: bool = false # the ground's shader reads the cascades itself (Vulkan); no sun pass
var ter_sun_tgt: Target = null # that buffer, at the frame's size
var ter_sun_refl: Target = null # and at the reflection's, which is smaller
var ter_sun_dumped: bool = false
@ -423,6 +424,11 @@ function terrain_init_finish() -> void {
# draw every patch with one tier's program (what each tier costs over a whole frame);
# R3D_NOSPLIT goes back to the single program that holds both tiers.
if Os.has_env("R3D_TFAST") { defs = defs + "#define TFAST_" + Os.env("R3D_TFAST") + "\n" }
# Vulkan reads the cascades inside the ground's own shader and draws no separate sun pass
# (terrain.frag, SUN_INLINE): one rasterisation of the patches instead of two, in the frame and in
# the reflection. R3D_SUN_PASS=1 keeps the pass there too, for comparing.
ter_sun_inline = gpu_kind == GPU_VK and not Os.has_env("R3D_SUN_PASS")
if ter_sun_inline { defs = defs + "#define SUN_INLINE\n" }
ter_prog = r3d_program("terrain.vert", "terrain.frag", defs)
ter_prog_far = r3d_program("terrain.vert", "terrain.frag", defs + "#define FAR_ONLY\n")
ter_prog_near = r3d_program("terrain.vert", "terrain.frag", defs + "#define NEAR_ONLY\n")
@ -487,9 +493,12 @@ function terrain_bind_prog(p: int) -> void {
# The ground reads its sun visibility out of the buffer tersun.frag filled, and has no
# use for the cascade array shadow_bind just put on this unit; leaving both bound under
# one unit is undefined ground, so the array comes off first.
gpu_tex_unit(15)
gpu_tex_bind(GPU_TEX2D_ARRAY, 0)
r3d_bind_2d(p, "u_sunshadow", 15, ter_sun_tex)
# (With the read inline, the array shadow_bind put there is exactly what the ground wants.)
if not ter_sun_inline {
gpu_tex_unit(15)
gpu_tex_bind(GPU_TEX2D_ARRAY, 0)
r3d_bind_2d(p, "u_sunshadow", 15, ter_sun_tex)
}
}
# The visibility buffer for the size being drawn into. The reflection is rendered at its
@ -559,6 +568,7 @@ function terrain_sun_pass(w: int, h: int, depth: int) -> Target {
}
function terrain_sun_prepare() -> void {
if ter_sun_inline { return }
ter_sun_tex = terrain_sun_pass(post_w, post_h, post_hdr.depth).color
ter_sun_done = true
}
@ -571,7 +581,7 @@ function terrain_draw() -> void {
var vw = post_w
var vh = post_h
if ter_reflect { vw = water_refl.w; vh = water_refl.h }
if not ter_sun_done {
if not ter_sun_done and not ter_sun_inline {
var dep = post_hdr.depth
if ter_reflect { dep = water_refl.depth }
ter_sun_tex = terrain_sun_pass(vw, vh, dep).color