First implementation of near-camera polygon tessellation, which surprisingly actually worked on the first try!

Currently still rather inefficient, making no use of GTE for interpolation yet. Still only one tessellation level too.

draw.h

@@ -331,6 +331,195 @@ static INLINE void draw_quadstrip_textured(const ps1bsp_vertex_t *vertices, cons
     }
 }
 
+typedef struct _TMPVERT
+{
+    int16_t vx, vy, vz, vpad;
+    uint8_t r, g, b, cpad;
+    uint8_t u, v;
+    uint16_t pad;
+} TMPVERT;
+
+#define copyVertFast(dst, pv, v)  \
+    setColorFast(&(dst)->r, &(pv)->r); \
+    setColorFast(&(dst)->vx, &(v)->vx); \
+    setColorFast(&(dst)->vz, &(v)->vz); \
+    setUVFast(&(dst)->u, &(pv)->u);
+
+#define lerpVert(dst, src0, src1) \
+    (dst)->vx = (int16_t)(((int32_t)(src0)->vx + (int32_t)(src1)->vx) >> 1); \
+    (dst)->vy = (int16_t)(((int32_t)(src0)->vy + (int32_t)(src1)->vy) >> 1); \
+    (dst)->vz = (int16_t)(((int32_t)(src0)->vz + (int32_t)(src1)->vz) >> 1); \
+    (dst)->r = (uint8_t)(((uint16_t)(src0)->r + (uint16_t)(src1)->r) >> 1); \
+    (dst)->g = (uint8_t)(((uint16_t)(src0)->g + (uint16_t)(src1)->g) >> 1); \
+    (dst)->b = (uint8_t)(((uint16_t)(src0)->b + (uint16_t)(src1)->b) >> 1); \
+    (dst)->u = (uint8_t)(((uint16_t)(src0)->u + (uint16_t)(src1)->u) >> 1); \
+    (dst)->v = (uint8_t)(((uint16_t)(src0)->v + (uint16_t)(src1)->v) >> 1);
+
+#define blitVert(dst, src)  \
+    setColorFast(&(dst)->x, &(src)->vx); \
+    setColorFast(&(dst)->r, &(src)->r); \
+    setUVFast(&(dst)->u, &(src)->u);
+
+static INLINE void draw_quadstrip_tess2(const ps1bsp_vertex_t *vertices, const ps1bsp_polyvertex_t *polyVerts, u_char numVerts, u_short tpage, u_long *ot)
+{
+    const ps1bsp_polyvertex_t *pv0, *pv1, *pv2, *pv3;
+    const ps1bsp_vertex_t *v0, *v1, *v2, *v3;
+    u_char i0, i1, i2, i3;
+    u_char head = 0;
+    u_char tail = numVerts;
+
+    // Initialize the first two vertices
+    i2 = --tail;
+    i3 = head++;
+
+    TMPVERT *tmp = (TMPVERT*)(scratchpad);
+   
+    // Normally a quad strip would have (N-2)/2 quads, but we might end up with a sole triangle at the end which will be drawn as a collapsed quad
+    // NOTE: testing has shown that the PS1 is faster just rendering quads and accepting the odd collapsed quad, rather than being clever with pointer comparisons and drawing a single triangle at the end.
+    u_char numQuads = (numVerts - 1) >> 1;
+    for (u_char quadIdx = 0; quadIdx < numQuads; ++quadIdx)
+    {
+        i0 = i2;
+        i1 = i3;
+        i2 = --tail;
+        i3 = head++;
+
+        pv0 = &polyVerts[i0];
+        pv1 = &polyVerts[i1];
+        pv2 = &polyVerts[i2];
+        pv3 = &polyVerts[i3];
+
+        v0 = &vertices[pv0->index];
+        v1 = &vertices[pv1->index];
+        v2 = &vertices[pv2->index];
+        v3 = &vertices[pv3->index];
+
+        copyVertFast(&tmp[0], pv0, v0);
+        copyVertFast(&tmp[2], pv1, v1);
+        copyVertFast(&tmp[6], pv2, v2);
+        copyVertFast(&tmp[8], pv3, v3);
+
+        lerpVert(&tmp[1], &tmp[0], &tmp[2]);
+        lerpVert(&tmp[3], &tmp[0], &tmp[6]);
+        lerpVert(&tmp[5], &tmp[2], &tmp[8]);
+        lerpVert(&tmp[7], &tmp[6], &tmp[8]);
+        lerpVert(&tmp[4], &tmp[3], &tmp[5]);
+
+        // Transform the vertices in groups of three
+        gte_ldv3(&tmp[0], &tmp[1], &tmp[2]);
+        gte_rtpt();
+        gte_stsxy0(&tmp[0].vx);
+        gte_stsxy1(&tmp[1].vx);
+        gte_stsxy2(&tmp[2].vx);
+
+        gte_ldv3(&tmp[3], &tmp[4], &tmp[5]);
+        gte_rtpt();
+        gte_stsxy0(&tmp[3].vx);
+        gte_stsxy1(&tmp[4].vx);
+        gte_stsxy2(&tmp[5].vx);
+
+        gte_ldv3(&tmp[6], &tmp[7], &tmp[8]);
+        gte_rtpt();
+        gte_stsxy0(&tmp[6].vx);
+        gte_stsxy1(&tmp[7].vx);
+        gte_stsxy2(&tmp[8].vx);
+
+        // Draw the first quad
+        POLY_GT4 *poly = (POLY_GT4*)mem_prim(sizeof(POLY_GT4));
+        setColorFast(&poly->x0, &tmp[0].vx);
+        setColorFast(&poly->r0, &tmp[0].r);
+        setUVFast(&poly->u0, &tmp[0].u);
+        poly->clut = quake_clut;
+
+        setColorFast(&poly->x1, &tmp[3].vx);
+        setColorFast(&poly->r1, &tmp[3].r);
+        setUVFast(&poly->u1, &tmp[3].u);
+        poly->tpage = tpage;
+
+        setColorFast(&poly->x2, &tmp[1].vx);
+        setColorFast(&poly->r2, &tmp[1].r);
+        setUVFast(&poly->u2, &tmp[1].u);
+
+        setColorFast(&poly->x3, &tmp[4].vx);
+        setColorFast(&poly->r3, &tmp[4].r);
+        setUVFast(&poly->u3, &tmp[4].u);
+
+        setPolyGT4(poly);
+        addPrim(ot, poly);
+
+        // Second quad
+        poly = (POLY_GT4*)mem_prim(sizeof(POLY_GT4));
+        setColorFast(&poly->x0, &tmp[1].vx);
+        setColorFast(&poly->r0, &tmp[1].r);
+        setUVFast(&poly->u0, &tmp[1].u);
+        poly->clut = quake_clut;
+
+        setColorFast(&poly->x1, &tmp[4].vx);
+        setColorFast(&poly->r1, &tmp[4].r);
+        setUVFast(&poly->u1, &tmp[4].u);
+        poly->tpage = tpage;
+
+        setColorFast(&poly->x2, &tmp[2].vx);
+        setColorFast(&poly->r2, &tmp[2].r);
+        setUVFast(&poly->u2, &tmp[2].u);
+
+        setColorFast(&poly->x3, &tmp[5].vx);
+        setColorFast(&poly->r3, &tmp[5].r);
+        setUVFast(&poly->u3, &tmp[5].u);
+
+        setPolyGT4(poly);
+        addPrim(ot, poly);
+
+        // Third quad
+        poly = (POLY_GT4*)mem_prim(sizeof(POLY_GT4));
+        setColorFast(&poly->x0, &tmp[3].vx);
+        setColorFast(&poly->r0, &tmp[3].r);
+        setUVFast(&poly->u0, &tmp[3].u);
+        poly->clut = quake_clut;
+
+        setColorFast(&poly->x1, &tmp[6].vx);
+        setColorFast(&poly->r1, &tmp[6].r);
+        setUVFast(&poly->u1, &tmp[6].u);
+        poly->tpage = tpage;
+
+        setColorFast(&poly->x2, &tmp[4].vx);
+        setColorFast(&poly->r2, &tmp[4].r);
+        setUVFast(&poly->u2, &tmp[4].u);
+
+        setColorFast(&poly->x3, &tmp[7].vx);
+        setColorFast(&poly->r3, &tmp[7].r);
+        setUVFast(&poly->u3, &tmp[7].u);
+
+        setPolyGT4(poly);
+        addPrim(ot, poly);
+
+        // Fourth quad
+        poly = (POLY_GT4*)mem_prim(sizeof(POLY_GT4));
+        setColorFast(&poly->x0, &tmp[4].vx);
+        setColorFast(&poly->r0, &tmp[4].r);
+        setUVFast(&poly->u0, &tmp[4].u);
+        poly->clut = quake_clut;
+
+        setColorFast(&poly->x1, &tmp[7].vx);
+        setColorFast(&poly->r1, &tmp[7].r);
+        setUVFast(&poly->u1, &tmp[7].u);
+        poly->tpage = tpage;
+
+        setColorFast(&poly->x2, &tmp[5].vx);
+        setColorFast(&poly->r2, &tmp[5].r);
+        setUVFast(&poly->u2, &tmp[5].u);
+
+        setColorFast(&poly->x3, &tmp[8].vx);
+        setColorFast(&poly->r3, &tmp[8].r);
+        setUVFast(&poly->u3, &tmp[8].u);
+
+        setPolyGT4(poly);
+        addPrim(ot, poly);
+
+        polyCount += 4;
+    }
+}
+
 static INLINE void draw_quadstrip_water(const ps1bsp_vertex_t *vertices, const ps1bsp_polyvertex_t *polyVerts, u_char numVerts, u_short tpage, u_char semiTrans, u_long *ot)
 {
     // Draw the face as a quad strip

ps1bsp.h

@@ -63,7 +63,7 @@ typedef struct
 // This matches the SVECTOR data type; we can use the extra padding to store some more data.
 typedef struct
 {
-	short x, y, z;
+	short vx, vy, vz;
 	short pad;
 } ps1bsp_vertex_t;
 

world.c

@@ -144,7 +144,7 @@ static void world_drawface_textured(const world_t *world, const ps1bsp_face_t *f
     const ps1bsp_texture_t *texture = &world->textures[face->textureId];
     const ps1bsp_polygon_t* poly = &world->polygons[face->firstPolygon];
 
-    // u_char tess = face->flags & 3;
+    u_char tess = face->flags & 3;
     // if (tess)
     // {
     //     world_drawface_flat(world, face, &colors[tess - 1], ot);
@@ -170,6 +170,9 @@ static void world_drawface_textured(const world_t *world, const ps1bsp_face_t *f
                 draw_triangle_textured(world->vertices, polyVertices, texture->tpage, ot);
                 break;
             default:
+                if (tess)
+                    draw_quadstrip_tess2(world->vertices, polyVertices, poly->numPolyVertices, texture->tpage, ot);
+                else
                     draw_quadstrip_textured(world->vertices, polyVertices, poly->numPolyVertices, texture->tpage, ot);
                 break;
             }