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OpenGL opengl normal mapped objects alongside non-normal mapped objects

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Hey all,


Relatively vague question here:


So, I've been toying around with normal mapping and am able to correctly render normal mapped objects in their own little program. However, when I try to implement this into another project, one that also has objects that don't use normal maps, the normal mapped objects don't render at all. The object is there, it just is rendered invisible/transparent. I don't receive any error at all, and am a little stumped where to begin debugging. After some brunt debugging attempts like rendering only the normal mapped object, and not calling the render function for the other objects (still has the same outcome) I'm beginning to wonder if I'm going wrong with the VAO when loading the objects. This is just a guess though. 


I've not posted any code here because even a simplified version would require two sets of building, rendering, and shading processes, since I'm really uncertain where I'm going wrong. If certain snippets would help, please let me know and I'll be happy to post them.


Anyhow, I was curious if anyone would know offhand why this may be a problem or has dealt with something similar. Should I be using separate VAOs, should I be clearing it between render calls or something along those lines? Does this perhaps have nothing to do with my VAO?

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So my post is similarly vague ...


How do you use the VAOs/VBOs? From the OP I assume that you generate 1 VAO, bind it, and let it alone forever. Then all handling of VBOs is to be done "manually" whenever a draw call is prepared, inclusive enabling/disabling of vertex attributes. Anyway, the entire relevant draw state should be specified with each (sub-)mesh to render, so that your low-level layer of rendering is able to compare what is needed with the current set-up (i.e. there is no rely on some draw state being set or being cleared). So (especially w.r.t. your case) switching VBOs and enabling/disabling the vertex attributes is done on a per mesh basis. If, on the hand, you use one VAO per VBO constellation, e.g. one for normal mapped and one for not normal mapped objects, things are not really different except that the draw state then is given with less parameters: It specifies the entire vertex assembly state by a single reference instead of a bunch of parameters.


How have you detected that "The object is there, it just is rendered invisible/transparent"? I meant, there is a difference between "no pixel is rastered", "all rastered pixels are discarded", and "the pixels are alpha blended with an alpha of zero". In all cases the objects is not on the screen, but the reasons are very different. For example, what happens if you take the normal mapping fragment shader and short-circuit all computations but simply put out a constant color with alpha 1? What happens if you short-circuit computations of the normals in the vertex shader?

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Thanks for the quick reply. And no worries about a vague answer, especially since I didn't post any details, that's mostly what I was looking for anyhow (and you're still rather specific smile.png).


And, I should have been clearer with my comment "The object is there, it just is rendered invisible/transparent". Also, now when looking into this, I'm a little more confused. To explain, where the object ought to be rendered, there's a transparent hole in the game world in the shape of the object (you can see through the ground, characters, etc). However, it occurs to me now, the odd thing is that you see all the way to the skybox,..which confuses me as there is no difference I can see between the skybox and the ground, rendering-wise, so I'm not sure why that still shows behind, and not just the glClear color . The order of rendering the objects doesn't affect this.


It's probably important to note here, that I'm only outputting a vec3 for color in the normal-mapped object's shader, and not tinkering with the alpha. Whereas the other object's shader I do output a vec4 with the alpha value.


And, upon a little further investigation, the difference with the skybox and the skybox's shader, is that, unlike the other objects, I'm not using a texture array for it. 


It's rather late for me, but I'll try to pin things down more accurately tomorrow by using your suggestions with the shader's normal values. I have a few more ideas now, I'll test out to try to pin this down a little closer.


Thanks for the help Haegarr. If I still can't sort things out, I'll go ahead and post the whole shebang here (in a simplified form, of course). I realize it can be frustrating for anyone to help without seeing the code.



Alright, I toyed with things a little this morning, and it looks like it's probably a trivial error somewhere. In my simple program, I'm easily able to render an object with a normal map alongside an object without and they both display fine. My method is the exact same as my larger project, as far as I can tell, but obviously I'm making a small mistake somewhere. But, it shouldn't be in the way that I'm doing things. So, somewhere in my larger program I'm doing something that is resulting in the transparent object.


I'm kind of back to where I started, but at least I've ruled out that it's something to do with my method of rendering things. I'm still totally open to ideas though, as I would like to integrate normal mapping into my larger project, and I'm still at a bit of a loss where to look for the mistake (it's rather a large project, for me at least). I'll likely just start going through things with a fine toothed comb. But, first some food and family. Happy Thanksgiving all!

Edited by Misantes

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Also, to update a little. I did test the shader to output an alpha value of 1.0f, as well as testing it to simply output a vec4(1,1,1,1), both to the same effect as before.

I should also correct my earlier statement about the render order not affecting things. If the objects are rendered after the normal mapped object, that is when they give the transparent "hole" appearance. But, if the normal mapped object is rendered first, then there's no visual indication that the object is rendered at all. 


An interesting development though:

I'm not sure if I'm "short circuiting" the vertex shader correctly, as I'm not 100% certain how to go about that. The vertex shader  transposes the vertex tangent, bitangent and normal in cameraspace and then multiplies that by the light direction. I've tried various inputs and outputs and none effectively change the outcome. However, I've cut out the normal calculations entirely and simply output the light direction tangents without multiplying them by the tangents/bitangents and normals (so, effectively just passing the light direction through the vertex shader) and interestingly, this makes the normal mapped object render at the location of the object rendered before it, and with the previous object's fragment shader. So...that confuses the hell out of me. Just to note, this happens whether I call glDisableVertexAttribArray() on the previous object's arrays or not. 

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