Consider 8 triangles on the screen like so:
+-+-+
|/|/|
+-+-+
|/|/|
+-+-+
Draw the left 4 triangles front-facing, the right 4 triangles back-facing.
Flip the top 4 triangles in the geometry shader (swap the first and last
vertex). In the fragment shader write different colors according to
gl_FrontFacing. The result should be a 2x2 checkerboard.
Signed-off-by: Fabian Bieler <[email protected]>
---
.../execution/geometry/two-side.shader_test | 86 ++++++++++++++++++++++
1 file changed, 86 insertions(+)
create mode 100644 tests/spec/glsl-1.50/execution/geometry/two-side.shader_test
diff --git a/tests/spec/glsl-1.50/execution/geometry/two-side.shader_test
b/tests/spec/glsl-1.50/execution/geometry/two-side.shader_test
new file mode 100644
index 0000000..8afd239
--- /dev/null
+++ b/tests/spec/glsl-1.50/execution/geometry/two-side.shader_test
@@ -0,0 +1,86 @@
+# Consider 8 triangles on the screen like so:
+#
+# +-+-+
+# |/|/|
+# +-+-+
+# |/|/|
+# +-+-+
+#
+# Draw the left 4 triangles front-facing, the right 4 triangles back-facing.
+# Flip the top 4 triangles in the geometry shader (swap the first and last
+# vertex). In the fragment shader write different colors according to
+# gl_FrontFacing. The result should be a 2x2 checkerboard.
+[require]
+GL >= 3.2
+GLSL >= 1.50
+
+[vertex shader]
+attribute vec4 vertex;
+
+void main()
+{
+ gl_Position = vertex;
+}
+
+[geometry shader]
+layout(triangles) in;
+layout(triangle_strip, max_vertices = 3) out;
+
+void main()
+{
+ float y = gl_in[0].gl_Position.y + gl_in[1].gl_Position.y +
+ gl_in[2].gl_Position.y;
+ for (int i = 0; i < 3; i++) {
+ /* Flip the triangles in the upper half of the screen. */
+ if (y > 0.0)
+ gl_Position = gl_in[2 - i].gl_Position;
+ else
+ gl_Position = gl_in[i].gl_Position;
+ EmitVertex();
+ }
+}
+
+[fragment shader]
+void main()
+{
+ if (gl_FrontFacing)
+ gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);
+ else
+ gl_FragColor = vec4(0.0, 0.0, 1.0, 1.0);
+}
+
+[vertex data]
+vertex/float/2
+-1.0 -1.0
+ 0.0 -1.0
+ 0.0 0.0
+-1.0 -1.0
+ 0.0 0.0
+-1.0 0.0
+ 0.0 -1.0
+ 0.0 0.0
+ 1.0 0.0
+ 0.0 -1.0
+ 1.0 0.0
+ 1.0 -1.0
+-1.0 0.0
+ 0.0 0.0
+ 0.0 1.0
+-1.0 0.0
+ 0.0 1.0
+-1.0 1.0
+ 0.0 0.0
+ 0.0 1.0
+ 1.0 1.0
+ 0.0 0.0
+ 1.0 1.0
+ 1.0 0.0
+
+
+[test]
+enable GL_VERTEX_PROGRAM_TWO_SIDE
+draw arrays GL_TRIANGLES 0 24
+relative probe rgba (0.25, 0.25) (0.0, 1.0, 0.0, 1.0)
+relative probe rgba (0.75, 0.25) (0.0, 0.0, 1.0, 1.0)
+relative probe rgba (0.25, 0.75) (0.0, 0.0, 1.0, 1.0)
+relative probe rgba (0.75, 0.75) (0.0, 1.0, 0.0, 1.0)
--
1.8.3.2
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