src/gallium/auxiliary/util/u_sampler.c

   1 /**************************************************************************
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   3  * Copyright 2010 VMware, Inc.
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  16  * of the Software.
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  26  **************************************************************************/
  27
  28
  29 #include "u_format.h"
  30 #include "u_sampler.h"
  31
  32
  33 static void
  34 default_template(struct pipe_sampler_view *view,
  35                  const struct pipe_resource *texture,
  36                  enum pipe_format format,
  37                  unsigned expand_green_blue)
  38 {
  39    /* XXX: Check if format is compatible with texture->format.
  40     */
  41
  42    view->format = format;
  43    view->u.tex.first_level = 0;
  44    view->u.tex.last_level = texture->last_level;
  45    view->u.tex.first_layer = 0;
  46    view->u.tex.last_layer = texture->target == PIPE_TEXTURE_3D ?
  47                                texture->depth0 - 1 : texture->array_size - 1;
  48    view->swizzle_r = PIPE_SWIZZLE_RED;
  49    view->swizzle_g = PIPE_SWIZZLE_GREEN;
  50    view->swizzle_b = PIPE_SWIZZLE_BLUE;
  51    view->swizzle_a = PIPE_SWIZZLE_ALPHA;
  52
  53    /* Override default green and blue component expansion to the requested
  54     * one.
  55     *
  56     * Gallium expands nonexistent components to (0,0,0,1), DX9 expands
  57     * to (1,1,1,1).  Since alpha is always expanded to 1, and red is
  58     * always present, we only really care about green and blue
  59     * components.
  60     *
  61     * To make it look less hackish, one would have to add
  62     * UTIL_FORMAT_SWIZZLE_EXPAND to indicate components for expansion
  63     * and then override without exceptions or favoring one component
  64     * over another.
  65     */
  66    if (format != PIPE_FORMAT_A8_UNORM) {
  67       const struct util_format_description *desc = util_format_description(format);
  68
  69       assert(desc);
  70       if (desc) {
  71          if (desc->swizzle[1] == UTIL_FORMAT_SWIZZLE_0) {
  72             view->swizzle_g = expand_green_blue;
  73          }
  74          if (desc->swizzle[2] == UTIL_FORMAT_SWIZZLE_0) {
  75             view->swizzle_b = expand_green_blue;
  76          }
  77       }
  78    }
  79 }
  80
  81 void
  82 u_sampler_view_default_template(struct pipe_sampler_view *view,
  83                                 const struct pipe_resource *texture,
  84                                 enum pipe_format format)
  85 {
  86    /* Expand to (0, 0, 0, 1) */
  87    default_template(view,
  88                     texture,
  89                     format,
  90                     PIPE_SWIZZLE_ZERO);
  91 }
  92
  93 void
  94 u_sampler_view_default_dx9_template(struct pipe_sampler_view *view,
  95                                     const struct pipe_resource *texture,
  96                                     enum pipe_format format)
  97 {
  98    /* Expand to (1, 1, 1, 1) */
  99    default_template(view,
 100                     texture,
 101                     format,
 102                     PIPE_SWIZZLE_ONE);
 103 }