Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Hopefully this will clear up some of your confusion, I used an older version of the spec. for simplicity, newer versions have two additional stages (tessellation control / evaluation) so the discussion is a little more complicated.</p> <h2><a href="http://www.opengl.org/registry/doc/glspec33.core.20100311.pdf" rel="nofollow">OpenGL 3.3 (Core Profile)</a> - 2.11. Vertex Shaders - pp. 80</h2> <blockquote> <p>Texture Access</p> <blockquote> <p>Shaders have the ability to do a lookup into a texture map. The maximum number of texture image units available to vertex, geometry, or fragment shaders are respectively the values of the implementation-dependent constants <code>GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS</code>, <code>GL_MAX_GEOMETRY_TEXTURE_IMAGE_UNITS</code>, and <code>GL_MAX_TEXTURE_IMAGE_UNITS</code>. The vertex shader, geometry shader, and fragment shader combined cannot use more than the value of <code>GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS</code> texture image units. If more than one of the vertex shader, geometry shader, and fragment processing stage access the same texture image unit, each such access counts separately against the <code>GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS</code> limit.</p> </blockquote> </blockquote> <p>The limit is imposed based on the number of unique samplers used in each stage. Two sampler uniforms with different names but which reference the same texture unit are effectively the same as far as usage determination is concerned. Usage refers to doing something like <code>texture (sampler, coords)</code>, if that was not already obvious. Merely declaring a sampler and assigning it a value is not going to bring you any closer to the implementation-defined limit, you actually have to <strong><em>use</em></strong> the sampler at run-time and if it has the same value as another used sampler in the same stage it does not count.</p> <p>As for using the same texture object multiple times, no this is not what the <code>GL_MAX_..._IMAGE_UNITS</code> limit is all about. You could bind the same texture to all 48 texture units (minimum implementation requirement in GL3.3 - this effectively mandates at least 16 textures per-stage) if you wanted, this limit refers to the number of different samplers you use (again, see above) in a shader stage. You might actually want to bind the same texture to multiple texture units if you need to use it once with nearest neighbor filtering and another time with linear or a different wrap state.</p> <p>If you want to know what behavior to expect on all drivers/hardware, always consult the formal OpenGL specification. I cherry picked the relevant information for you, but it would do you well to learn how to search through it for important details in the future. Every specification since OpenGL 1.0 is freely available from: <a href="http://www.opengl.org/registry/" rel="nofollow">http://www.opengl.org/registry/</a>.</p>
    singulars
    1. This table or related slice is empty.
    1. POUsing a single texture image unit with multiple sampler uniforms
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USAndon M. Coleman
    1. USAndon M. Coleman
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POUsing a single texture image unit with multiple sampler uniforms
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThanks for the excellent reply! I was under the impression that the enumerations passed to `glActiveTexture` (and thus also sampler uniform values) corresponded directly to TIUs, which was causing my confusion. So just to clarify, using a texture through the same binding point (`glUniform` value) in multiple shader stages is perfectly fine, as long as the per stage and combined limits are observed, since the driver actually uses 2 different TIUs behind the scenes?
      singulars
      1. PO
      1. USbcrist
    2. COEverything else is correct though. As long as you respect the per-stage limits and overall limits on TIUs you will be good to go. As mentioned before, `GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS` has a default implementation minimum just large enough to ensure that each stage can have its own set of 16 unique textures. There is nothing wrong with re-using the same texture image unit in multiple stages, but it will count against the combined limit at run-time.
      singulars
      1. PO
      1. USAndon M. Coleman
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload