fix rotated sprites

1 files changed, 13 insertions, 12 deletions

diff --git a/teensy/teensy_renderer.c b/teensy/teensy_renderer.c
index 61710a2..ea61163 100644
--- a/teensy/teensy_renderer.c
+++ b/teensy/teensy_renderer.c
@@ -202,20 +202,21 @@ void ty_draw_image_rot(
     ty_Vec2i offset,
     double rot
 ) {
-    double s = sin(rot);
-    double c = cos(rot);
- 
-    // x1 = c*x - s*y
-    // y1 = s*x + c*y
+    double s = sin(-rot);
+    double c = cos(-rot);
 
-    // FIXME: the corners of the rotated image get cut off.
-    for (int img_y = 0; img_y < img.height; img_y++) {
-        for (int img_x = 0; img_x < img.width; img_x++) {
-            double pixel_x = img_x + offset.x;
-            double pixel_y = img_y + offset.y;
+    int blit_width  = ceil(img.width * fabs(c) + img.height * fabs(s));
+    int blit_height = ceil(img.width * fabs(s) + img.height * fabs(c));
 
-            int dx = floor(pixel_x * c - pixel_y * s - offset.x);
-            int dy = floor(pixel_x * s + pixel_y * c - offset.y);
+    int startx = -blit_width / 2;
+    int starty = -blit_height / 2;
+    int endx = (blit_width + 1) / 2;
+    int endy = (blit_height + 1) / 2;
+
+    for (int img_y = starty; img_y < endy; img_y++) {
+        for (int img_x = startx; img_x < endx; img_x++) {
+            int dx = floor(img_x * c - img_y * s - offset.x);
+            int dy = floor(img_x * s + img_y * c - offset.y);
 
             if (dx < 0 || dx >= img.width || dy < 0 || dy >= img.height)
                 continue;