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perf(render3d): a depth prepass for the near tree foliage

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Needle-card crowns are many cut-out quads deep and a discarding shader turns early depth
rejection off, so every card behind the front one ran the full lighting shader. The near
tree LODs now write depth first (depth.frag, the same alpha coverage test), terrain under
them is rejected before shading, and the lit pass draws them with no discard and an equal
depth test (invariant gl_Position). R3D_NOPREPASS=1 restores the old path.

Dense forest on a Windows PC: 61 -> 78 fps at 3840x2160, 116 -> 164 fps at 1920x1080.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
Orkun ÇAKILKAYA 2026-09-13 04:18:38 +03:00
parent 21bc611455
commit d6ffdfa638
6 changed files with 123 additions and 1 deletions
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20
packages/ludic.render3d/render.ludic
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@ -26,6 +26,12 @@ var r3d_debug_max: bool = false
var r3d_cloud_shadow: int = 0x3F000000 # 0.5
var r3d_clip_y: int = 0xCF000000 # -2^31: no clipping
# R3D_NOPREPASS=1: light the foliage the old way, every card behind the front one included
var r3d_prepass_env: int = -1
function r3d_prepass_off() -> bool {
if r3d_prepass_env < 0 { r3d_prepass_env = 0; if Os.has_env("R3D_NOPREPASS") { r3d_prepass_env = 1 } }
return r3d_prepass_env == 1
}
function fog_bind(prog: int) -> void {
u_f(gl_uniform(prog, "u_clip_y"), r3d_clip_y)
u_f(gl_uniform(prog, "u_spec_scale"), F_ONE)
@ -158,6 +164,19 @@ function r3d_frame(time: int) -> void {
if water_on and not r3d_no_refl { prof_begin("water reflection"); water_reflection_pass(); prof_end() }
prof_cpu_mark("reflection")
post_begin_scene()
# the near tree foliage lays its depth down before anything is shaded, so the terrain
# under the stands and the cards behind the front ones are rejected before lighting.
# It has to come straight after post_begin_scene: terrain_sun_prepare binds its own
# target, and depth drawn after it lands in the sun buffer, not the scene's.
if not r3d_prepass_off() {
prof_begin("foliage prepass")
gl_color_mask(0, 0, 0, 0)
scatter_draw_depth()
gl_color_mask(1, 1, 1, 1)
prof_end()
sc_prepass = true
}
prof_cpu_mark("foliage prepass")
prof_begin("terrain sun")
terrain_sun_prepare()
prof_end()
@ -168,6 +187,7 @@ function r3d_frame(time: int) -> void {
prof_begin("scene (vegetation)")
scene_draw()
prof_end()
sc_prepass = false
prof_cpu_mark("vegetation")
prof_begin("grass")
grass_draw()