[add] alpha support to image class

2 files changed, 11 insertions, 14 deletions

diff --git a/src/application.lisp b/src/application.lisp
index 6869a56..3b531c9 100644
--- a/src/application.lisp
+++ b/src/application.lisp
@@ -116,7 +116,7 @@ those objects are currently part of the scene tree."
   (gl:clear :color-buffer-bit)
   (gl:enable :blend)
   (gl:blend-func :src-alpha :one-minus-src-alpha )
-  (dolist (unit (application-scene app))
+  (dolist (unit (reverse (application-scene app)))
     (render unit))
   (sdl2:gl-swap-window (application-window app))
   (sleep (frame-wait app)))
diff --git a/src/interactive/image.lisp b/src/interactive/image.lisp
index 1b3a817..644c06e 100644
--- a/src/interactive/image.lisp
+++ b/src/interactive/image.lisp
@@ -6,18 +6,9 @@
   "Cached for later cleanup.")
 (defvar *image-vao* nil)
 
-(defvar *image-count* 0
-  "Used by finalizers to determin if the shader should be destroyed.")
-
-(defun image-finalizer ()
-  "executed after a image has been reclaimed by gc. decrements image
-count and destroys shader-program if necessary."
-  (decf *image-count*)
-  (unless (plusp *image-count*)
-    ))
-
 (defclass/std image (unit interactive)
-  ((texture :ri :std (error "A image requires a texture."))))
+  ((texture :ri :std (error "A image requires a texture."))
+   (alpha :std 1.0)))
 
 (defun make-shared-image-gpu-objects ()
   (unless *image-shader-program*
@@ -31,8 +22,10 @@ count and destroys shader-program if necessary."
                vert))) ;color
            '(:fragment
              ((tc :vec2))
-             ((tex :sampler-2d))
+             ((tex :sampler-2d)
+              (alpha :float))
              ((let ((frag  (vari:texture tex tc)))
+                (setf (aref frag 3) (vari:clamp 0 (* alpha (aref frag 3)) 1))
                 (if (< (aref frag 3) 0.01)
                     (vari:discard)
                     frag))))))
@@ -77,7 +70,7 @@ count and destroys shader-program if necessary."
     (make-shared-image-gpu-objects)))
 
 (defmethod render ((image image))
-  (with-slots (texture) image
+  (with-slots (texture alpha) image
     (gl:active-texture 0)
     (gl:bind-texture :texture-2d (texture-id texture))
     (gl:use-program *image-shader-program*)
@@ -85,6 +78,10 @@ count and destroys shader-program if necessary."
      *image-shader-program*
      (gl:get-uniform-location *image-shader-program* "TRANSFORM")
      (projected-matrix image))
+    (gl:program-uniformf
+     *image-shader-program*
+     (gl:get-uniform-location *image-shader-program* "ALPHA")
+     alpha)
     (gl:bind-vertex-array *image-vao*)    
     (gl:draw-arrays :triangles 0 6)
     (gl:bind-vertex-array 0)))