torus.c: Lighting effect is distorted when object is scaled up/down

When torus object is scaled up/down via glScalef call the lighting
effect is incorrectly expressed on render target because normals'
length is also changed when vertices are scaled up/down.

This patch enables "automatic normalization" of normals, which
is one of well-known ways to avoid this kind of distortion.

Reference:
www.opengl.org/sdk/docs/man2/xhtml/glScale.xml

Notes

 If scale factors other than 1 are applied to the modelview matrix
 and lighting is enabled, lighting often appears wrong.
 In that case, enable automatic normalization of normals by
 calling glEnable with the argument GL_NORMALIZE.

Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/egl/opengles1/torus.c b/src/egl/opengles1/torus.c
index 8f262b53..ccf53d19 100644
--- a/src/egl/opengles1/torus.c
+++ b/src/egl/opengles1/torus.c
@@ -358,6 +358,11 @@ init(void)
 
    make_texture();
    glEnable(GL_TEXTURE_2D);
+
+   /* Enable automatic normalizing to get proper lighting when torus is
+    * scaled down via glScalef
+    */
+   glEnable(GL_NORMALIZE);
 }