Databases
StackOverflow2013
Postsdbo
POTroubles parsing Wavefront .obj texture coordinates
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POTroubles parsing Wavefront .obj texture coordinates
    primarykey
    data
    text
    <p>I'm coding my own .obj parser in objc for OpenGL ES 2.0 to get a better understanding on how this OpenGLES thing works. Loading the vertices and showing a model with vertex colors on it works like a charm. Just a small note: I'm using an index buffer.</p> <p>The real problem is the mapping of the textures atm. As you'll see a little bit more down below, my texture isn't mapped the way it should be. </p> <p>Here's how I think the .obj format works, please correct me if I'm wrong: the "f"-lines describe a face where the number before a slash defines the index of the vertex and the number after the slash defines a texture coordinate.</p> <p>Consider the following .obj file (exported by Cinema 4D):</p> <pre><code>v -75 75 -50 v 75 75 -50 v -75 -75 -50 v 75 -75 -50 vt 0 0 vt 0 1 vt 1 1 vt 1 0 f 4/3 3/2 1/1 f 2/4 4/3 1/1 </code></pre> <p>And the following texture:</p> <p><img src="https://i.stack.imgur.com/lyOgh.png" alt="512x512 Texture"></p> <p>Now, when I position the vertices in OpenGL ES 3D space and try to map the texture coordinates to each individual vertex, the mapping goes wrong. I could fix this by moving around some of the texture coordinate values but I realise this isn't the way to do it. I also tried to edit some of my .obj exporter settings to flip axises and/or uv mapping around but non of them result in a correct mapping. Is there something I'm missing in my theory concerning the .obj file format? One thing I might say already: I read yesterday that the coordinate system of the .obj format defines topleft as the anchor point of a texture. So I fixed that already in my parsing.</p> <p>Here's a small summary with the current situation: Update: the coordinate system of the texture is the actual .obj texture coordinate system and NOT OpenGL's coordinate system. I translate the coordinates in my parsing algorithm to counter this.</p> <p><img src="https://i.stack.imgur.com/FW4e1.png" alt="Summary"></p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USpolyclick
    1. USpolyclick
    plurals
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POTroubles parsing Wavefront .obj texture coordinates
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POTroubles parsing Wavefront .obj texture coordinates
      1. This table or related slice is empty.
      1. VTUpMod
    1. COAdded clarification on the coordinate system.
      singulars
      1. POTroubles parsing Wavefront .obj texture coordinates
      1. USpolyclick
    2. COHave a closer look at how the "v" and "vt" values in the .obj file correlate. OpenGL does not handle texture coords (and normals) the same way they are respresented in the OBJ file. So, without "moving around some of the texture coordinate values", you map the bottom-left point of your texture to the top-right vertex and vice versa. Remember that you cannot do texture coord indexing independently from vertex indexing in OpenGL. See http://stackoverflow.com/questions/4233152/how-to-setup-calculate-texturebuffer-in-gltexcoordpointer-when-importing-from-ob
      singulars
      1. POTroubles parsing Wavefront .obj texture coordinates
      1. USThalur
    3. COyou found the solution for this?
      singulars
      1. POTroubles parsing Wavefront .obj texture coordinates
      1. USAshika Umanga Umagiliya
 

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