Reorganize VShaderWrapper.render_fill

manimlib/shader_wrapper.py

@@ -327,8 +327,19 @@ class VShaderWrapper(ShaderWrapper):
         original_fbo = self.ctx.fbo
         texture_fbo, depth_texture_fbo, texture_vao = self.fill_canvas
 
+        # First, draw the border for antialiasing
+        self.fill_border_vao.render()
+
+        # Render to a separate texture, due to strange alpha compositing
+        # for the blended winding calculation
         texture_fbo.clear()
         texture_fbo.use()
+
+        # Be sure not to apply depth test while rendering fill
+        # but set it back to where it was after
+        apply_depth_test = bool(gl.glGetBooleanv(gl.GL_DEPTH_TEST))
+
+        self.ctx.disable(moderngl.DEPTH_TEST)
         gl.glBlendFuncSeparate(
             # Ordinary blending for colors
             gl.GL_SRC_ALPHA, gl.GL_ONE_MINUS_SRC_ALPHA,
@@ -337,10 +348,6 @@ class VShaderWrapper(ShaderWrapper):
             gl.GL_ONE_MINUS_DST_ALPHA, gl.GL_ONE,
         )
 
-        # Be sure not to apply depth test while rendering fill
-        # but set it back to where it was after
-        apply_depth_test = bool(gl.glGetBooleanv(gl.GL_DEPTH_TEST))
-        self.ctx.disable(moderngl.DEPTH_TEST)
         self.fill_vao.render()
         if apply_depth_test:
             depth_texture_fbo.clear(1.0)
@@ -350,20 +357,15 @@ class VShaderWrapper(ShaderWrapper):
             self.fill_depth_vao.render()
             self.ctx.enable(moderngl.DEPTH_TEST)
 
-        # Border width is used for antialiasing. Take the maximum between these
-        # two alphas, before compositing back to the rest of the scene
-        gl.glBlendFuncSeparate(
-            gl.GL_SRC_ALPHA, gl.GL_ONE_MINUS_SRC_ALPHA,
-            gl.GL_ONE, gl.GL_ZERO
-        )
-        gl.glBlendEquationSeparate(gl.GL_FUNC_ADD, gl.GL_MAX)
-        self.fill_border_vao.render()
 
         original_fbo.use()
-        gl.glBlendFunc(gl.GL_SRC_ALPHA, gl.GL_ONE_MINUS_SRC_ALPHA)
+        gl.glBlendFunc(gl.GL_ONE, gl.GL_ONE_MINUS_SRC_ALPHA)
         gl.glBlendEquation(gl.GL_FUNC_ADD)
         texture_vao.render()
 
+        gl.glBlendFunc(gl.GL_SRC_ALPHA, gl.GL_ONE_MINUS_SRC_ALPHA)
+        gl.glBlendEquation(gl.GL_FUNC_ADD)
+
     def render(self):
         if self.stroke_behind:
             self.render_stroke()

manimlib/utils/shaders.py

@@ -157,47 +157,48 @@ def get_fill_canvas(ctx: moderngl.Context) -> Tuple[Framebuffer, VertexArray]:
     texture_fbo = ctx.framebuffer(texture)
     depth_texture_fbo = ctx.framebuffer(depth_texture)
 
+    simple_vert = '''
+        #version 330
+
+        in vec2 texcoord;
+        out vec2 uv;
+
+        void main() {
+            gl_Position = vec4((2.0 * texcoord - 1.0), 0.0, 1.0);
+            uv = texcoord;
+        }
+    '''
+    alpha_adjust_frag = '''
+        #version 330
+
+        uniform sampler2D Texture;
+        uniform sampler2D DepthTexture;
+
+        in vec2 uv;
+        out vec4 color;
+
+        void main() {
+            color = texture(Texture, uv);
+            if(color.a == 0) discard;
+
+            // Counteract scaling in fill frag
+            color.a *= 1.06;
+
+            gl_FragDepth = texture(DepthTexture, uv)[0];
+        }
+    '''
     simple_program = ctx.program(
-        vertex_shader='''
+        vertex_shader=simple_vert,
-            #version 330
+        fragment_shader=alpha_adjust_frag,
-
-            in vec2 texcoord;
-            out vec2 uv;
-
-            void main() {
-                gl_Position = vec4((2.0 * texcoord - 1.0), 0.0, 1.0);
-                uv = texcoord;
-            }
-        ''',
-        fragment_shader='''
-            #version 330
-
-            uniform sampler2D Texture;
-            uniform sampler2D DepthTexture;
-
-            in vec2 uv;
-            out vec4 color;
-
-            void main() {
-                color = texture(Texture, uv);
-                if(color.a == 0) discard;
-
-                // Counteract scaling in fill frag
-                color *= 1.06;
-
-                gl_FragDepth = texture(DepthTexture, uv)[0];
-            }
-        ''',
     )
 
     simple_program['Texture'].value = get_texture_id(texture)
     simple_program['DepthTexture'].value = get_texture_id(depth_texture)
 
     verts = np.array([[0, 0], [0, 1], [1, 0], [1, 1]])
+    simple_vbo = ctx.buffer(verts.astype('f4').tobytes())
     fill_texture_vao = ctx.simple_vertex_array(
-        simple_program,
+        simple_program, simple_vbo, 'texcoord',
-        ctx.buffer(verts.astype('f4').tobytes()),
-        'texcoord',
         mode=moderngl.TRIANGLE_STRIP
     )
     return (texture_fbo, depth_texture_fbo, fill_texture_vao)