/*
-blender for the Gameboy Advance
-Copyright (C) 2021 John Tsiombikas <nuclear@member.fsf.org>
+gbajam22 entry for the Gameboy Advance
+Copyright (C) 2022 John Tsiombikas <nuclear@mutantstargoat.com>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
/* d = 1.0 / tan(fov/2) */
#define PROJ_D 0x20000
+/* near Z = 0.5 */
+#define NEAR_Z 0x10000
void xgl_draw(int prim, const struct xvertex *varr, int vcount)
{
}
while(vcount >= prim) {
- cidx = varr->cidx;
+ cidx = 0xff;//varr->cidx;
xform(xv, varr, mat[mtop]);
xform_norm(xv, varr, mat[mtop]);
- if(xv->nz > 0) {
- /* backface */
- varr += prim;
- vcount -= prim;
- continue;
- }
+ /* backfacing check */
+ if(xv->nz > 0) goto skip_poly;
+ /*
if(opt & XGL_LIGHTING) {
ndotl = (xv->nx >> 8) * ldir[0] + (xv->ny >> 8) * ldir[1] + (xv->nz >> 8) * ldir[2];
if(ndotl < 0) ndotl = 0;
cidx = 128 + (ndotl >> 9);
if(cidx > 255) cidx = 255;
}
+ */
- xv->x = (xv->x << 1) / (xv->z >> 8); /* assume aspect: ~2 */
- xv->y = (xv->y << 2) / (xv->z >> 8); /* the shift is * PROJ_D */
- /* projection result is 24.8 */
- /* viewport */
- pv->x = (((xv->x + 0x100) >> 1) * vp[2]) + (vp[0] << 8);
- pv->y = (((0x100 - xv->y) >> 1) * vp[3]) + (vp[1] << 8);
- varr++;
-
- for(i=1; i<prim; i++) {
- xform(xv + i, varr, mat[mtop]);
-
+ for(i=0; i<prim; i++) {
+ if(i > 0) {
+ xform(xv + i, varr + i, mat[mtop]);
+ }
xv[i].x = (xv[i].x << 1) / (xv[i].z >> 8); /* assume aspect: ~2 */
xv[i].y = (xv[i].y << 2) / (xv[i].z >> 8); /* the shift is * PROJ_D */
- /* projection result is 24.8 */
+ /* transform result is 24.8 */
+ }
+
+ /* clip against near plane */
+
+
+ for(i=0; i<prim; i++) {
/* viewport */
pv[i].x = (((xv[i].x + 0x100) >> 1) * vp[2]) + (vp[0] << 8);
pv[i].y = (((0x100 - xv[i].y) >> 1) * vp[3]) + (vp[1] << 8);
- varr++;
}
- vcount -= prim;
polyfill_flat(pv, prim, cidx);
+skip_poly:
+ varr += prim;
+ vcount -= prim;
}
}
#ifndef ALT_LCLIP
clip_line((int*)&xv[0].x, (int*)&xv[0].y, (int*)&xv[1].x, (int*)&xv[1].y, vp[0], vp[1], vp[2] - 1, vp[3] - 1);
#endif
- draw_line(xv[0].x, xv[0].y, xv[1].x, xv[1].y, varr[-2].cidx);
+ draw_line(xv[0].x, xv[0].y, xv[1].x, xv[1].y, 0xff);
}
}
{
mat[mtop][12] = mat[mtop][13] = 0;
}
+
+#define ISECT_NEAR(v0, v1) ((((v0)->z - NEAR_Z) << 8) / (((v0)->z - (v1)->z) >> 8))
+
+#define LERP_VATTR(res, v0, v1, t) \
+ do { \
+ (res)->x = (v0)->x + (((v1)->x - (v0)->x) >> 8) * (t); \
+ (res)->y = (v0)->y + (((v1)->y - (v0)->y) >> 8) * (t); \
+ (res)->z = (v0)->z + (((v1)->z - (v0)->z) >> 8) * (t); \
+ (res)->nx = (v0)->nx + (((v1)->nx - (v0)->nx) >> 8) * (t); \
+ (res)->ny = (v0)->ny + (((v1)->ny - (v0)->ny) >> 8) * (t); \
+ (res)->nz = (v0)->nz + (((v1)->nz - (v0)->nz) >> 8) * (t); \
+ (res)->tx = (v0)->tx + (((v1)->tx - (v0)->tx) >> 8) * (t); \
+ (res)->ty = (v0)->ty + (((v1)->ty - (v0)->ty) >> 8) * (t); \
+ (res)->lit = (v0)->lit + (((v1)->lit - (v0)->lit) >> 8) * (t); \
+ } while(0)
+
+static int clip_edge_near(struct xvertex *poly, int *vnumptr, struct xvertex *v0, struct xvertex *v1)
+{
+ int vnum = *vnumptr;
+ int in0, in1;
+ int32_t t;
+ struct xvertex *vptr;
+
+ in0 = v0->z >= NEAR_Z ? 1 : 0;
+ in1 = v1->z >= NEAR_Z ? 1 : 0;
+
+ if(in0) {
+ /* start inside */
+ if(in1) {
+ /* all inside */
+ poly[vnum++] = *v1; /* append v1 */
+ *vnumptr = vnum;
+ return 1;
+ } else {
+ /* going out */
+ vptr = poly + vnum;
+ t = ISECT_NEAR(v0, v1); /* 24:8 */
+ LERP_VATTR(vptr, v0, v1, t);
+ ++vnum; /* append new vertex on the intersection point */
+ }
+ } else {
+ /* start outside */
+ if(in1) {
+ /* going in */
+ vptr = poly + vnum;
+ t = ISECT_NEAR(v0, v1);
+ LERP_VATTR(vptr, v0, v1, t);
+ ++vnum; /* append new vertex ... */
+ /* then append v1 */
+ poly[vnum++] = *v1;
+ } else {
+ /* all outside */
+ return -1;
+ }
+ }
+
+ *vnumptr = vnum;
+ return 0;
+}
+
+/* special case near-plane clipper */
+int xgl_clip_near(struct xvertex *vout, int *voutnum, struct xvertex *vin, int vnum)
+{
+ int i, nextidx, res;
+ int edges_clipped = 0;
+
+ *voutnum = 0;
+
+ for(i=0; i<vnum; i++) {
+ nextidx = i + 1;
+ if(nextidx >= vnum) nextidx = 0;
+ res = clip_edge_near(vout, voutnum, vin + i, vin + nextidx);
+ if(res == 0) {
+ ++edges_clipped;
+ }
+ }
+
+ if(*voutnum <= 0) return -1;
+ return edges_clipped > 0 ? 0 : 1;
+}
projects / gbajam22 / blobdiff