src/gallium/auxiliary/util/u_sampler.c

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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->first_level = 0;
  44    view->last_level = texture->last_level;
  45    view->swizzle_r = PIPE_SWIZZLE_RED;
  46    view->swizzle_g = PIPE_SWIZZLE_GREEN;
  47    view->swizzle_b = PIPE_SWIZZLE_BLUE;
  48    view->swizzle_a = PIPE_SWIZZLE_ALPHA;
  49
  50    /* Override default green and blue component expansion to the requested
  51     * one.
  52     *
  53     * Gallium expands nonexistent components to (0,0,0,1), DX9 expands
  54     * to (1,1,1,1).  Since alpha is always expanded to 1, and red is
  55     * always present, we only really care about green and blue
  56     * components.
  57     *
  58     * To make it look less hackish, one would have to add
  59     * UTIL_FORMAT_SWIZZLE_EXPAND to indicate components for expansion
  60     * and then override without exceptions or favoring one component
  61     * over another.
  62     */
  63    if (format != PIPE_FORMAT_A8_UNORM) {
  64       const struct util_format_description *desc = util_format_description(format);
  65
  66       assert(desc);
  67       if (desc) {
  68          if (desc->swizzle[1] == UTIL_FORMAT_SWIZZLE_0) {
  69             view->swizzle_g = expand_green_blue;
  70          }
  71          if (desc->swizzle[2] == UTIL_FORMAT_SWIZZLE_0) {
  72             view->swizzle_b = expand_green_blue;
  73          }
  74       }
  75    }
  76 }
  77
  78 void
  79 u_sampler_view_default_template(struct pipe_sampler_view *view,
  80                                 const struct pipe_resource *texture,
  81                                 enum pipe_format format)
  82 {
  83    /* Expand to (0, 0, 0, 1) */
  84    default_template(view,
  85                     texture,
  86                     format,
  87                     PIPE_SWIZZLE_ZERO);
  88 }
  89
  90 void
  91 u_sampler_view_default_dx9_template(struct pipe_sampler_view *view,
  92                                     const struct pipe_resource *texture,
  93                                     enum pipe_format format)
  94 {
  95    /* Expand to (1, 1, 1, 1) */
  96    default_template(view,
  97                     texture,
  98                     format,
  99                     PIPE_SWIZZLE_ONE);
 100 }