+
+void vox_sky_grad(struct voxscape *vox, uint32_t chor, uint32_t ctop)
+{
+ int i, j, colheight, t;
+ int r0, g0, b0, r1, g1, b1, r, g, b;
+ int d = vox->fbheight - 250;
+ uint32_t *grad, *fbptr;
+
+ grad = alloca(vox->fbheight * sizeof *grad);
+
+ r0 = ctop >> 16;
+ g0 = (ctop >> 8) & 0xff;
+ b0 = ctop & 0xff;
+ r1 = chor >> 16;
+ g1 = (chor >> 8) & 0xff;
+ b1 = chor & 0xff;
+
+ for(i=0; i<d; i++) {
+ t = (i << 8) / d;
+ r = ((r0 << 8) + (r1 - r0) * t) >> 8;
+ g = ((g0 << 8) + (g1 - g0) * t) >> 8;
+ b = ((b0 << 8) + (b1 - b0) * t) >> 8;
+ assert(r >= 0 && r < 256);
+ assert(g >= 0 && g < 256);
+ assert(b >= 0 && b < 256);
+ grad[i] = (r << 16) | (g << 8) | b;
+ }
+ for(i=d; i<vox->fbheight; i++) {
+ grad[i] = chor;
+ }
+
+ for(i=0; i<vox->fbwidth; i++) {
+ fbptr = vox->fb + i;
+ colheight = vox->fbheight - vox->coltop[i];
+ for(j=0; j<colheight; j++) {
+ *fbptr = grad[j];
+ fbptr += vox->fbwidth;
+ }
+ }
+}