Atlas resize shader without geometry shader (#2698)

Author: einarf

arcade/context.py

@@ -131,9 +131,13 @@ def __init__(
         )
         # Atlas shaders
         self.atlas_resize_program: Program = self.load_program(
-            vertex_shader=":system:shaders/atlas/resize_vs.glsl",
-            geometry_shader=":system:shaders/atlas/resize_gs.glsl",
-            fragment_shader=":system:shaders/atlas/resize_fs.glsl",
+            # NOTE: This is the geo shader version of the atlas resize program.
+            # vertex_shader=":system:shaders/atlas/resize_vs.glsl",
+            # geometry_shader=":system:shaders/atlas/resize_gs.glsl",
+            # fragment_shader=":system:shaders/atlas/resize_fs.glsl",
+            # Vertex and fragment shader version
+            vertex_shader=":system:shaders/atlas/resize_simple_vs.glsl",
+            fragment_shader=":system:shaders/atlas/resize_simple_fs.glsl",
         )
         self.atlas_resize_program["atlas_old"] = 0  # Configure texture channels
         self.atlas_resize_program["atlas_new"] = 1

arcade/resources/system/shaders/atlas/resize_fs.glsl

@@ -1,6 +1,7 @@
 #version 330
 
-// The old atlas texture.
+// The old atlas texture. We copy sections to the new atlas texture
+// by render into an fbo with the target texture as the color attachment.
 uniform sampler2D atlas_old;
 
 out vec4 fragColor;

arcade/resources/system/shaders/atlas/resize_gs.glsl

@@ -4,11 +4,13 @@
 
 #include :system:shaders/lib/sprite.glsl
 
-// Old and new texture coordiantes
+// Old and new texture coordinates
 uniform sampler2D atlas_old;
 uniform sampler2D atlas_new;
+
 uniform sampler2D texcoords_old;
 uniform sampler2D texcoords_new;
+
 uniform mat4 projection;
 uniform float border;
 
@@ -33,7 +35,7 @@ void main() {
     // absolute value of the diagonal * size + border * 2
     vec2 size = abs(new_uv3 - new_uv0) * vec2(size_new) + vec2(border * 2.0);
 
-    // We need to offset the old coordiantes by border size
+    // We need to offset the old coordinates by border size
     vec2 pix_offset = vec2(border) / vec2(size_old);
     // (
     //     0.015625, 0.015625,  # minus, minus

arcade/resources/system/shaders/atlas/resize_simple_fs.glsl

@@ -0,0 +1,13 @@
+#version 330
+// Atlas resize without geometry shader
+
+// The old atlas texture. We copy sections to the new atlas texture
+// by render into an fbo with the target texture as the color attachment.
+uniform sampler2D atlas_old;
+
+out vec4 fragColor;
+in vec2 uv;
+
+void main() {
+    fragColor = texture(atlas_old, uv);
+}

arcade/resources/system/shaders/atlas/resize_simple_vs.glsl

@@ -0,0 +1,76 @@
+#version 330
+// Atlas resize without geometry shader
+
+// The render target for this program is the new
+// texture atlas texture
+
+#include :system:shaders/lib/sprite.glsl
+
+// Old and new texture coordinates
+uniform sampler2D atlas_old;
+uniform sampler2D atlas_new;
+
+uniform sampler2D texcoords_old;
+uniform sampler2D texcoords_new;
+
+uniform mat4 projection;
+uniform float border;
+
+out vec2 uv;
+
+void main() {
+    // Get the texture sizes
+    ivec2 size_old = textureSize(atlas_old, 0).xy;
+    ivec2 size_new = textureSize(atlas_new, 0).xy;
+
+    // Read texture coordinates from UV texture here
+    int texture_id = gl_VertexID / 6;
+    vec2 old_uv0, old_uv1, old_uv2, old_uv3;
+    getSpriteUVs(texcoords_old, texture_id, old_uv0, old_uv1, old_uv2, old_uv3);
+    vec2 new_uv0, new_uv1, new_uv2, new_uv3;
+    getSpriteUVs(texcoords_new, texture_id, new_uv0, new_uv1, new_uv2, new_uv3);
+
+    // Lower left corner flipped * size - border
+    vec2 pos = vec2(new_uv2.x, 1.0 - new_uv2.y) * vec2(size_new) - vec2(border);
+    // absolute value of the diagonal * size + border * 2
+    vec2 size = abs(new_uv3 - new_uv0) * vec2(size_new) + vec2(border * 2.0);
+
+    // We need to offset the old coordinates by border size
+    vec2 pix_offset = vec2(border) / vec2(size_old);
+
+    // Emit two triangles over 6 vertices
+    switch (gl_VertexID % 6) {
+        // First triangle
+        case 0:
+            // upper left
+            uv = old_uv0 - pix_offset;
+            gl_Position = projection * vec4(pos + vec2(0.0, size.y), 0.0, 1.0);
+            break;
+        case 1:
+            // lower left   
+            uv = old_uv2 + vec2(-pix_offset.x, pix_offset.y);
+            gl_Position = projection * vec4(pos, 0.0, 1.0);
+            break;
+        case 2:
+            // upper right
+            uv = old_uv1 + vec2(pix_offset.x, -pix_offset.y);
+            gl_Position = projection * vec4(pos + vec2(size.x, size.y), 0.0, 1.0);
+            break;
+        // Second triangle
+        case 3:
+            // lower left
+            uv = old_uv2 + vec2(-pix_offset.x, pix_offset.y);
+            gl_Position = projection * vec4(pos, 0.0, 1.0);
+            break;
+        case 4:
+            // upper right
+            uv = old_uv1 + vec2(pix_offset.x, -pix_offset.y);
+            gl_Position = projection * vec4(pos + vec2(size.x, size.y), 0.0, 1.0);
+            break;
+        case 5:
+            // lower right
+            uv = old_uv3 + pix_offset;
+            gl_Position = projection * vec4(pos + vec2(size.x, 0.0), 0.0, 1.0);
+            break;
+    }
+}

arcade/texture_atlas/atlas_default.py

@@ -103,7 +103,7 @@ def __init__(
         self,
         size: tuple[int, int],
         *,
-        border: int = 1,
+        border: int = 2,
         textures: Sequence[Texture] | None = None,
         auto_resize: bool = True,
         ctx: ArcadeContext | None = None,
@@ -667,8 +667,7 @@ def resize(self, size: tuple[int, int], force=False) -> None:
             force:
                 Force a resize even if the size is the same
         """
-        # LOG.info("[%s] Resizing atlas from %s to %s", id(self), self._size, size)
-        # print("Resizing atlas from", self._size, "to", size)
+        print("Resizing atlas from", self._size, "to", size)
 
         # Only resize if the size actually changed
         if size == self._size and not force:
@@ -732,8 +731,9 @@ def resize(self, size: tuple[int, int], force=False) -> None:
             with self._ctx.enabled_only():
                 self._ctx.geometry_empty.render(
                     self._ctx.atlas_resize_program,
-                    mode=self._ctx.POINTS,
-                    vertices=self.max_width,
+                    mode=self._ctx.TRIANGLES,
+                    # Two triangles per texture
+                    vertices=UV_TEXTURE_WIDTH * self._capacity * 6,
                 )
 
         # duration = time.perf_counter() - resize_start
@@ -746,7 +746,7 @@ def rebuild(self) -> None:
         This method also tries to organize the textures more efficiently ordering them by size.
         The texture ids will persist so the sprite list doesn't need to be rebuilt.
         """
-        # LOG.info("Rebuilding atlas")
+        print("Rebuilding atlas")
 
         # Hold a reference to the old textures
         textures = self.textures

tests/unit/atlas/test_basics.py

@@ -11,7 +11,7 @@ def test_create(ctx, common):
     assert atlas.width == 100
     assert atlas.height == 200
     assert atlas.size == (100, 200)
-    assert atlas.border == 1
+    assert atlas.border == 2
     assert atlas.auto_resize is True
     assert isinstance(atlas.max_size, tuple)
     assert atlas.max_size > (0, 0)