graphics: texture: Add black, white, gray, and flat convenience textures.

1 files changed, 40 insertions, 0 deletions

diff --git a/chickadee/graphics/texture.scm b/chickadee/graphics/texture.scm
index 5b46af1..b3a9985 100644
--- a/chickadee/graphics/texture.scm
+++ b/chickadee/graphics/texture.scm
@@ -49,6 +49,10 @@
             texture-gl-rect
             texture-gl-tex-rect
             null-texture
+            black-texture
+            white-texture
+            gray-texture
+            flat-texture
             g:texture-0
             g:texture-1
             g:texture-2
@@ -317,6 +321,42 @@ magnification.  Valid values are 'nearest and 'linear.  By default,
       (surface->texture surface min-filter mag-filter wrap-s wrap-t
                         transparent-color flip?))))
 
+(define (black-texture)
+  null-texture)
+
+(define %white-texture
+  (delay
+    (make-texture (u32vector #xffffffff #xffffffff #xffffffff #xffffffff)
+                  2 2)))
+
+(define (white-texture)
+  (force %white-texture))
+
+(define %gray-texture
+  (delay
+    (make-texture (u32vector #xff808080 #xff808080 #xff808080 #xff808080)
+                  2 2)))
+
+(define (gray-texture)
+  (force %gray-texture))
+
+;; A "flat" normal map, in tangent space.  It's like the identity
+;; property for normals. The colors are used to store 3D tangent space
+;; vectors, with positive Z being "up".  Each coordinate is in the
+;; [-1,1] range and then remapped to an 8-bit color channel in the
+;; 0-255 range.  Thus, 0 maps to 127 or #x80, -1 maps to 0, and 1 maps
+;; to 255.  The color values are in ABGR ordering.  A flat tangent
+;; normal is (0, 0, 1), which is encoded as the color #xffff8080.
+;; Such a value means that a mesh's vertex normals remain completely
+;; unchanged by this normal map.
+(define %flat-texture
+  (delay
+    (make-texture (u32vector #xffff8080 #xffff8080 #xffff8080 #xffff8080)
+     2 2)))
+
+(define (flat-texture)
+  (force %flat-texture))
+
 
 ;;;
 ;;; Texture Atlas