Add split depth buffer for world/overlay

[grits] / src / grits-opengl.c

diff --git a/src/grits-opengl.c b/src/grits-opengl.c
index 0e803baf3b5abd6a30e141bde022075254223123..861bfc933a8cd5a38674e926f6df6ebabd456b3f 100644 (file)
--- a/src/grits-opengl.c
+++ b/src/grits-opengl.c
@@ -40,6 +40,8 @@
 
 // #define ROAM_DEBUG
 
+#define OVERLAY_SLICE 0.01
+
 /* Tessellation, "finding intersecting triangles" */
 /* http://research.microsoft.com/pubs/70307/tr-2006-81.pdf */
 /* http://www.opengl.org/wiki/Alpha_Blending */
@@ -312,9 +314,10 @@ static void _draw_level(gpointer _level, gpointer _opengl)
                /* Enable depth and alpha for world levels */
                glEnable(GL_ALPHA_TEST);
                glAlphaFunc(GL_GREATER, 0.1);
+               glDepthRange(OVERLAY_SLICE, 1);
        } else {
-               /* Disable depth for Overlay/HUD levels */
-               glDepthMask(FALSE);
+               /* Draw overlay in front of world */
+               glDepthRange(0, OVERLAY_SLICE);
        }
 
        /* Start ortho */
@@ -512,6 +515,7 @@ static void grits_opengl_unproject(GritsViewer *_opengl,
                glReadPixels(px, py, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &tmp);
                pz = tmp;
        }
+       pz = (pz-OVERLAY_SLICE) * (1.0/(1-OVERLAY_SLICE));
        gluUnProject(px, py, pz,
                opengl->sphere->view->model,
                opengl->sphere->view->proj,