From 3a5463d158eff483a992c9792d771fb80db9aed0 Mon Sep 17 00:00:00 2001
From: Brian Paul <brianp@vmware.com>
Date: Mon, 12 Jan 2009 15:43:54 -0700
Subject: i965: fix broken glBitmap + depth test

When we use the do_blit_bitmap() function, it seems the fragment Z is always
1.0.  If depth testing is on, that means that bitmap fragments are often
occluded by other rendering.  So, the bitmap doesn't appear even if
rasterpos.Z==0.
The fix is to use the intel_texture_bitmap() path when depth testing is on.
Also, fix the incorrect Z coordinate.  It needs to be an NDC value in [-1,1].
---
 src/mesa/drivers/dri/intel/intel_pixel_bitmap.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

(limited to 'src/mesa/drivers')

diff --git a/src/mesa/drivers/dri/intel/intel_pixel_bitmap.c b/src/mesa/drivers/dri/intel/intel_pixel_bitmap.c
index 1d7f15f10a..3a01f63dc7 100644
--- a/src/mesa/drivers/dri/intel/intel_pixel_bitmap.c
+++ b/src/mesa/drivers/dri/intel/intel_pixel_bitmap.c
@@ -204,6 +204,14 @@ do_blit_bitmap( GLcontext *ctx,
    /* Update draw buffer bounds */
    _mesa_update_state(ctx);
 
+   if (ctx->Depth.Test) {
+      /* The blit path produces incorrect results when depth testing is on.
+       * It seems the blit Z coord is always 1.0 (the far plane) so fragments
+       * will likely be obscured by other, closer geometry.
+       */
+      return GL_FALSE;
+   }
+
    if (!dst)
        return GL_FALSE;
 
@@ -357,6 +365,7 @@ intel_texture_bitmap(GLcontext * ctx,
    GLubyte *unpacked_bitmap;
    GLubyte *a8_bitmap;
    int x, y;
+   GLfloat dst_z;
 
    /* We need a fragment program for the KIL effect */
    if (!ctx->Extensions.ARB_fragment_program ||
@@ -456,21 +465,24 @@ intel_texture_bitmap(GLcontext * ctx,
    intel_meta_set_passthrough_vertex_program(intel);
    intel_meta_set_passthrough_transform(intel);
 
+   /* convert rasterpos Z from [0,1] to NDC coord in [-1,1] */
+   dst_z = -1.0 + 2.0 * ctx->Current.RasterPos[2];
+
    vertices[0][0] = dst_x;
    vertices[0][1] = dst_y;
-   vertices[0][2] = ctx->Current.RasterPos[2];
+   vertices[0][2] = dst_z;
    vertices[0][3] = 1.0;
    vertices[1][0] = dst_x + width;
    vertices[1][1] = dst_y;
-   vertices[1][2] = ctx->Current.RasterPos[2];
+   vertices[1][2] = dst_z;
    vertices[1][3] = 1.0;
    vertices[2][0] = dst_x + width;
    vertices[2][1] = dst_y + height;
-   vertices[2][2] = ctx->Current.RasterPos[2];
+   vertices[2][2] = dst_z;
    vertices[2][3] = 1.0;
    vertices[3][0] = dst_x;
    vertices[3][1] = dst_y + height;
-   vertices[3][2] = ctx->Current.RasterPos[2];
+   vertices[3][2] = dst_z;
    vertices[3][3] = 1.0;
 
    texcoords[0][0] = 0.0;
-- 
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