zbuffered lines

diff --git a/src/gaw/polyfill.c b/src/gaw/polyfill.c
index f0355c1..e6a87f6 100644 (file)
--- a/src/gaw/polyfill.c
+++ b/src/gaw/polyfill.c
@@ -487,7 +487,7 @@ void draw_line_zbuf(struct pvertex *verts)
        int32_t x0, y0, x1, y1, z0, z1, z, dz, zslope;
        int i, dx, dy, x_inc, y_inc, error;
        uint32_t *fb = pfill_fb.pixels;
-       uint32_t *zptr;
+       uint32_t *zptr = pfill_zbuf;
        uint32_t color = PACK_RGB(verts[0].r, verts[0].g, verts[0].b);
 
        x0 = verts[0].x >> 8;
@@ -498,7 +498,7 @@ void draw_line_zbuf(struct pvertex *verts)
        z1 = verts[1].z;
 
        fb += y0 * pfill_fb.width + x0;
-       zptr = pfill_zbuf + y0 * pfill_fb.width + x0;
+       zptr += y0 * pfill_fb.width + x0;
 
        dx = x1 - x0;
        dy = y1 - y0;
@@ -517,8 +517,10 @@ void draw_line_zbuf(struct pvertex *verts)
                dy = -dy;
        }
 
+       z = z0;
+
        if(dx > dy) {
-               zslope = dx ? (dz << 8) / dx : 0;
+               zslope = dx ? (dz << 8) / (verts[1].x - verts[0].x) : 0;
                error = dy * 2 - dx;
                for(i=0; i<=dx; i++) {
                        if(z <= *zptr) {
@@ -537,7 +539,7 @@ void draw_line_zbuf(struct pvertex *verts)
                        z += zslope;
                }
        } else {
-               zslope = dy ? (dz << 8) / dy : 0;
+               zslope = dy ? (dz << 8) / (verts[1].y - verts[0].y) : 0;
                error = dx * 2 - dy;
                for(i=0; i<=dy; i++) {
                        if(z <= *zptr) {