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[glsl,vulkan] More comments in the bsp code

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And maybe a nano-optimization. Switching from (~side + 1) to (-side)
seems to give glsl a very tiny speed boost, but certainly doesn't hurt.
Looking at some assembly output for the three cases, the two hacks seem
to generate the same code as each other, but 3 instructions vs 6 for ?:.
While ?: is more generically robust, the hacks are tuned for the
knowledge side is either 0 or 1. The later xor might alter things, but
at least I now know that the hack (either version) is worthwhile.
This commit is contained in:
Bill Currie 2022-05-13 22:00:03 +09:00
parent bc82241e1c
commit beb05f28ff
2 changed files with 16 additions and 5 deletions
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9
libs/video/renderer/glsl/glsl_bsp.c
View file

@ -731,6 +731,7 @@ visit_leaf (mleaf_t *leaf)
R_StoreEfrags (leaf->efrags);
}
// 1 = back side, 0 = front side
static inline int
get_side (mnode_t *node)
{
@ -750,8 +751,10 @@ visit_node (glslbspctx_t *bctx, mnode_t *node, int side)
msurface_t *surf;
// sneaky hack for side = side ? SURF_PLANEBACK : 0;
side = (~side + 1) & SURF_PLANEBACK;
// draw stuff
// seems to be microscopically faster even on modern hardware
side = (-side) & SURF_PLANEBACK;
// chain any visible surfaces on the node that face the camera.
// not all nodes have any surfaces to draw (purely a split plane)
if ((c = node->numsurfaces)) {
surf = bctx->brush->surfaces + node->firstsurface;
for (; c; c--, surf++) {
@ -759,6 +762,8 @@ visit_node (glslbspctx_t *bctx, mnode_t *node, int side)
continue;
// side is either 0 or SURF_PLANEBACK
// if side and the surface facing differ, then the camera is
// on backside of the surface
if (side ^ (surf->flags & SURF_PLANEBACK))
continue; // wrong side

12
libs/video/renderer/vulkan/vulkan_bsp.c
View file

@ -638,11 +638,13 @@ R_DrawBrushModel (entity_t *e, vulkan_ctx_t *ctx)
static inline void
visit_leaf (mleaf_t *leaf)
{
// deal with model fragments in this leaf
// since this leaf will be rendered, any entities in the leaf also need
// to be rendered (the bsp tree doubles as an entity cull structure)
if (leaf->efrags)
R_StoreEfrags (leaf->efrags);
}
// 1 = back side, 0 = front side
static inline int
get_side (mnode_t *node)
{
@ -662,8 +664,10 @@ visit_node (mod_brush_t *brush, mnode_t *node, int side, vulkan_ctx_t *ctx)
msurface_t *surf;
// sneaky hack for side = side ? SURF_PLANEBACK : 0;
side = (~side + 1) & SURF_PLANEBACK;
// draw stuff
// seems to be microscopically faster even on modern hardware
side = (-side) & SURF_PLANEBACK;
// chain any visible surfaces on the node that face the camera.
// not all nodes have any surfaces to draw (purely a split plane)
if ((c = node->numsurfaces)) {
surf = brush->surfaces + node->firstsurface;
for (; c; c--, surf++) {
@ -671,6 +675,8 @@ visit_node (mod_brush_t *brush, mnode_t *node, int side, vulkan_ctx_t *ctx)
continue;
// side is either 0 or SURF_PLANEBACK
// if side and the surface facing differ, then the camera is
// on backside of the surface
if (side ^ (surf->flags & SURF_PLANEBACK))
continue; // wrong side