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norman784

OpenGL Issues loading textures

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I'm having issues loading textures, as I'm clueless on how to handle / load images maybe I missing something, but the past few days I just google a lot to try to find a solution. Well theres two issues I think, one I'm using Kotlin Native (EAP) and OpenGL wrapper / STB image, so I'm not quite sure wheres the issue, if someone with more experience could give me some hints on how to solve this issue?

The code is here, if I'm not mistaken the workflow is pretty straight forward, stbi_load returns the pixels of the image (as char array or byte array) and you need to pass those pixels directly to glTexImage2D, so a I'm missing something here it seems.

Regards

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9 hours ago, norman784 said:

if someone with more experience could give me some hints on how to solve this issue?

I would like to help but you haven't described anything about the issue that you're having nor the code that lead to this issue. The code that doesn't work is not the tutorial that you linked, right?

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Sorry I was not not clear, and yes, I'm porting the opengl tutorial to kotlin native, so the link that leads to github is my code that is not working, well the expected result is the next image as the rectangle texture

 

 logo.png.e4192b84bfdcc5c0e057307a6dd5776e.png

 

But the result that I'm having is this

1259763347_ScreenShot2018-06-13at11_44_14AM.png.585bd6c527648937b3d286789c1d4246.png

I'm not sure if is stbi_load, my image or the opengl code. But I'm doing some more test, this time in C (it will took me a while because I'm not used to C, besides is not that hard, the I don't know the tools).

Why I chose stb? because seems to be an easy to include a single header library into the projects, but if theres another recommended alternative to this library I'll try it.

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4 hours ago, norman784 said:

Ok, I get it work on C, so is matter of time when I find the issue in the Kotlin side.

From what I understand "Kotlin" is simply a library used to parse and retrieve the pixel data of image files (png, jpg etc...).

Since the result you get is a solid color I would suggest manually inspecting the byte array of data that it returns. It will be very easy to see if you see the same pixel data repeated over blocks of 4 or 3 bytes. If that's the case then the issue is indeed the image loading part with that library.

Edited by ChuckNovice

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Well I finally solve it, and no, Kotlin in a language that has interoperability with C, so in some cases the interop adds odd stuffs and also because is in early development (Kotlin native itself) doesn't have so much documentation about the matter.

For some reference about how it was solved check this issue.

Edit: this is the final result I was looking for

923782673_ScreenShot2018-06-13at7_13_19PM.png.f722cbb87654d920c94c4125b78abcc4.png

Edited by norman784

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      I tried to multiply some matrixes and so on, but without result and currently I've got no idea how to do that..
       
      Fragment of code looks like this:
      void DrawModel(Model.IModel model) { GL.glLoadIdentity(); GL.glPushMatrix(); this.SetSceneByCamera(); foreach (Model.IModelPart part in model.ModelParts) this.DrawPart(part); GL.glPopMatrix(); } void DrawPart(Model.IModelPart part) { bool draw = true; GL.glPushMatrix(); #region get part children Model.IModelPart child_top = part.GetChild("_top"); Model.IModelPart child_left = part.GetChild("_left"); Model.IModelPart child_right = part.GetChild("_right"); Model.IModelPart child_bottom = part.GetChild("_bottom"); #endregion get part children #region by part switch (part.PartTBase) { case Model.ModelPart.PartTypeBase.ALEIRON: { #region aleiron float moveBy = 0.0f; bool selected = false; switch (part.PartT) { case Model.ModelPart.PartType.ALEIRON_L: { selected = true; moveBy = this.GetFromValDic(part); moveBy *= -1; } break; } if (selected && child_left != null && child_right != null) { GL.glTranslatef(child_right.GetCentralPoint.X, child_right.GetCentralPoint.Y, child_right.GetCentralPoint.Z); GL.glRotatef(moveBy, child_left.GetCentralPoint.X - child_right.GetCentralPoint.X, child_left.GetCentralPoint.Y - child_right.GetCentralPoint.Y, child_left.GetCentralPoint.Z - child_right.GetCentralPoint.Z); GL.glTranslatef(-child_right.GetCentralPoint.X, -child_right.GetCentralPoint.Y, -child_right.GetCentralPoint.Z); } #endregion aleiron } break; } #endregion by part #region draw part if (!part.Visible) draw = false; if (draw) { GL.glBegin(GL.GL_TRIANGLES); for (int i = 0; i < part.ModelPoints.Count; i += 3) { if (part.ModelPoints[i].GetTexCoord != null) GL.glTexCoord3d((double)part.ModelPoints[i].GetTexCoord.X, (double)part.ModelPoints[i].GetTexCoord.Y, (double)part.ModelPoints[i].GetTexCoord.Z); GL.glVertex3f(part.ModelPoints[i].GetPoint.X, part.ModelPoints[i].GetPoint.Y, part.ModelPoints[i].GetPoint.Z); if (part.ModelPoints[i + 1].GetTexCoord != null) GL.glTexCoord3d((double)part.ModelPoints[i + 1].GetTexCoord.X, (double)part.ModelPoints[i + 1].GetTexCoord.Y, (double)part.ModelPoints[i + 1].GetTexCoord.Z); GL.glVertex3f(part.ModelPoints[i + 1].GetPoint.X, part.ModelPoints[i + 1].GetPoint.Y, part.ModelPoints[i + 1].GetPoint.Z); if (part.ModelPoints[i + 2].GetTexCoord != null) GL.glTexCoord3d((double)part.ModelPoints[i + 2].GetTexCoord.X, (double)part.ModelPoints[i + 2].GetTexCoord.Y, (double)part.ModelPoints[i + 2].GetTexCoord.Z); GL.glVertex3f(part.ModelPoints[i + 2].GetPoint.X, part.ModelPoints[i + 2].GetPoint.Y, part.ModelPoints[i + 2].GetPoint.Z); } GL.glEnd(); } #endregion draw part GL.glPopMatrix(); } What happens step by step:
      Prepare scene, set the model camera by current variables {user can move camera using keyboard and mouse in all directions}. Take model which contains all modelParts within and draw them one by one. Each part has its own type and subtype set by part name. Draw current part independently, get its child_left and child_right -> those are the balls by name. Get moveBy value which is angle. Every part has its own variable which is modified using keyboard like "press a, increase variable x for 5.0f", which in turn will rotate aleiron up by 5.0f. Move and rotate object by its children Draw part triangles {the part has its own list of triangles that are read from obj file}  
      When I compute the blue ball that is glued to its parent, I do exactly the same so it moves with the same manner:
      case Model.ModelPart.PartTypeBase.FLOW: { float moveBy = 0.0f; Model.IModelPart parent = part.GetParent(); if (parent != null) { moveBy = this.GetFromValDic(parent); if (parent.Reverse) moveBy *= -1.0f; child_left = parent.GetChild("_left"); child_right = parent.GetChild("_right"); } if (child_left != null && child_right != null) { GL.glGetFloatv(GL.GL_MODELVIEW_MATRIX, part.BeforeMove); GL.glTranslatef(child_right.GetCentralPoint.X, child_right.GetCentralPoint.Y, child_right.GetCentralPoint.Z); GL.glRotatef(moveBy, child_left.GetCentralPoint.X - child_right.GetCentralPoint.X, child_left.GetCentralPoint.Y - child_right.GetCentralPoint.Y, child_left.GetCentralPoint.Z - child_right.GetCentralPoint.Z); GL.glTranslatef(-child_right.GetCentralPoint.X, -child_right.GetCentralPoint.Y, -child_right.GetCentralPoint.Z); } } break;  
      Before move I read the model matrix using GL.glGetFloatv(GL.GL_MODEL_MATRIX, matrix), which gives me those values {red contains current model camera}:

      The blue ball has its own initial central point computed, and currently it is (x, y, z): 339.6048, 15.811758, -166.209473.
      As far as I'm concerned, the point world coordinates never change, only its matrix is moved and rotated around some point.
      So the final question is, how to calculate the same point world coordinates after the object is moved and rotated?
      PS:
      to visualize the problem, I've created new small box, which I placed on the center of the blue ball after it is moved upwards.
      The position of the box is written by eye - I just placed it couple of times and after x try, I managed to place it correctly using similar world coordinates:

      First one is from the left of the box, and the second one is from behind.
      The box world coordinates are (x, y, z): 340.745117f, 30.0f, -157.6322f, so according to original central point of blue ball it is a bit higher and closer to the center of the wing.
      Simply put, I need to: 
      take original central point of blue ball: 339.6048, 15.811758, -166.209473 after the movement and rotation of the blue ball is finished, apply some algorithm {like take something from modelview_matrix, multiply by something other} finally, after the algorithm is complete, in result I get 340.745117f, 30.0f, -157.6322f point {but now computed}, which is the central point in world matrix after movement. PS2: Sorry for long post, I tried to exactly explain what I'm dealing with.
       
      Thank you in advance for your help.
       
       
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