No need to recalculate the index inside each loop

Here's hoping Zig is smart enough (TM) to constant-ify all of these
@floatToInt(type, PlaneXXX) values.

1 files changed, 11 insertions, 15 deletions

diff --git a/src/render.zig b/src/render.zig
index ae9983c..00e65fd 100644
--- a/src/render.zig
+++ b/src/render.zig
@@ -329,22 +329,22 @@ pub fn Renderer(PlaneWidth: f32, PlaneHeight: f32) type {
                                 const constrained_top = std.math.floor(std.math.min(top_of_floor, lowest_drawn));
                                 const proj_height = cell.floor_height * nominal_length;
                                 const constrained_bottom = std.math.max(highest_drawn, top_of_floor - proj_height);
-                                const stop = @floatToInt(usize, PlaneHeight - constrained_bottom);
-                                var pix_y = @floatToInt(usize, std.math.ceil(std.math.max(PlaneHeight - constrained_top - 1, 0)));
+                                const stop = @floatToInt(usize, PlaneWidth * (PlaneHeight - constrained_bottom)) + col;
+                                const pix_y = @floatToInt(usize, std.math.ceil(std.math.max(PlaneHeight - constrained_top - 1, 0)));
+                                var pix_index = pix_y * @floatToInt(usize, PlaneWidth) + col;
                                 var texel_y: f32 = std.math.max((top_of_floor - constrained_top) / nominal_length, 0);
 
                                 // now we have what we need to draw the face,
                                 // and update the z-buffer. Note that it doesn't
                                 // matter which way we write to the z_buffer
                                 // here, walls are vertical!
-                                while (pix_y < stop) : ({
-                                    pix_y += 1;
+                                while (pix_index < stop) : ({
+                                    pix_index += @floatToInt(usize, PlaneWidth);
                                     texel_y += inv_nom_len;
                                 }) {
                                     const ty = @floatToInt(c_uint, std.math.modf(texel_y).fpart * constants.TextureDim);
                                     const texel = walls_image.getPixel(.{ .x = t_lower_off + texstrip, .y = ty });
 
-                                    const pix_index = pix_y * @floatToInt(usize, PlaneWidth) + col;
                                     pixels[pix_index] = texel;
                                     self.z_buffer[pix_index] = distance;
                                 }
@@ -355,22 +355,18 @@ pub fn Renderer(PlaneWidth: f32, PlaneHeight: f32) type {
                                 const proj_default_end = PlaneHeight / 2 + PlaneDist * (level.Cell.DEFAULT_HEIGHT - pheight) / distance;
                                 const constrained_top = std.math.min(lowest_drawn, proj_default_end);
                                 const constrained_bottom = std.math.max(bottom_of_ceiling, highest_drawn);
-                                const stop = @floatToInt(i32, PlaneHeight - constrained_bottom);
+                                const stop = @floatToInt(usize, PlaneWidth * (PlaneHeight - constrained_bottom)) + col;
                                 const t_upper_off = cell.upper_texture * td;
-                                var pix_y = @floatToInt(usize, std.math.ceil(std.math.max(PlaneHeight - constrained_top - 1, 0)));
-                                // TODO: Decide if textures should be pinned at
-                                // the top or bottom. Currently they are pinned
-                                // at the top. For bottom this would read:
-                                // constants.TextureDim - (constrained_top - constrained_bottom) / nominal_length
-                                var texel_y: f32 = (proj_default_end - constrained_top) / nominal_length;
-                                while (pix_y < stop) : ({
-                                    pix_y += 1;
+                                const pix_y = @floatToInt(usize, std.math.ceil(std.math.max(PlaneHeight - constrained_top - 1, 0)));
+                                var pix_index = pix_y * @floatToInt(usize, PlaneWidth) + col;
+                                var texel_y: f32 = constants.TextureDim - (constrained_top - constrained_bottom) / nominal_length;
+                                while (pix_index < stop) : ({
+                                    pix_index += @floatToInt(usize, PlaneWidth);
                                     texel_y += inv_nom_len;
                                 }) {
                                     const ty = @floatToInt(c_uint, std.math.modf(texel_y).fpart * constants.TextureDim);
                                     const texel = walls_image.getPixel(.{ .x = t_upper_off + texstrip, .y = ty });
 
-                                    const pix_index = pix_y * @floatToInt(usize, PlaneWidth) + col;
                                     pixels[pix_index] = texel;
                                     self.z_buffer[pix_index] = distance;
                                 }