# DX11 UV problem with FBX and DX11

This topic is 1669 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

Hello All!
Came by here today hoping somebody has some experience loading models into DX11 using the FBX SDK. I am
having a weird problem when I load in my texture coordinates. On some models, they render correctly while on others, they render with the "U" flipped. An example below:

The space ship is rendered correctly, while the planet texture is flipped. Both are using the same code to load them in, the only difference is that I am sending in different strings for where to fetch the file from.

I load in the vertices from FBX in the following manner:

	int counter = 0;
//Loop through the polygons
for (int p = 0; p < fbxMesh->GetPolygonCount(); p++)
{
//Loop through the three vertices within each polygon
for(int v = 0; v < fbxMesh->GetPolygonSize(p); v++)
{

const int controlPointIndex = fbxMesh->GetPolygonVertex(p, v);

VertexStruct vS;
vS.position = FBXD3DVector3(fbxMesh->GetControlPointAt(controlPointIndex));

FbxVector2 tex;
bool isMapped;
fbxMesh->GetPolygonVertexUV(p, v, lUVSetName, tex, isMapped);
vS.uv = D3DXVECTOR2(tex[0], -tex[1]);

FbxVector4 norm;
fbxMesh->GetPolygonVertexNormal(p, v, norm);
vS.normal = D3DXVECTOR3(-norm[0], -norm[1], -norm[2]);

m_Vertices.push_back(vS);

m_Indices.push_back(static_cast<unsigned int>(counter));

counter++;
}

}



Tried looking on the FBX forums but had no luck. I could hard code them individually but I was looking to create a system where all my resources are loaded. Any help would be greatly appreciated. Thanks!

##### Share on other sites

This is typical when using content from DCC packages in D3D. D3D specifies that V = 0 is the top of the texture and OpenGL specifies that V = 0 is the bottom, so you usually have to flip the V coordinates (and the bitangents!) when generating meshes for D3D.

##### Share on other sites

Thanks for the reply. Yes I understand that...however my problem seems to be with the 'U' coordinates. The planet is flipped ( so you have Asia on the western hemisphere and the Americas on the east.). The mesh was just a simple sphere that I exported from 3Ds Max, applied a mesh modifier, applied a texture to it and unwrapped it. The models I downloaded from TurboSquid. I tried 2 different artists and both loaded correctly. The same happened when I tried it on a cube.

Edited by JacobM

##### Share on other sites

Is your coordinate system handness coorect? 3DS Max is right-handed, while DX if left-handed.

If you export it as RHS, then in DX all of your triangles will be facing inward, causing back-face culling to cull the wrong triangles. Which means you are seeing the inside of the sphere, creating the apperance of U coordinate mirroring.

You can test this theory by rotating the sphere - if I'm correct, then it will appear to rotate in the wrong direction.

##### Share on other sites

Check you export settings. Probablly the problem is in the UVW mapping. Use the UVW modifination(if you're using 3ds max) and specify the mapping type. If you drag and drop the texture the default the mapping generated will be OGL style(not shure im always using UVW modifier). You can tell 3ds max to generate fliped UVs

##### Share on other sites

Thanks for the reply. Yes I understand that...however my problem seems to be with the 'U' coordinates. The planet is flipped ( so you have Asia on the western hemisphere and the Americas on the east.). The mesh was just a simple sphere that I exported from 3Ds Max, applied a mesh modifier, applied a texture to it and unwrapped it. The models I downloaded from TurboSquid. I tried 2 different artists and both loaded correctly. The same happened when I tried it on a cube.

##### Share on other sites

Satanir:

This is what I originally thought as well. However culling was turned on and it was culling the correct triangles. i inverted the mesh in 3Ds max and it indeed fixed the texture. But now i was seeing inside of the sphere. Also, if that was the case then i assume the spaceships textures would have been inverted as well, but they come out just fine.
But I am sure that the sphere is being drawn correctly so I am not understanding why I am getting such mixed results.

imoogiBG:
I have used the UV unwrap, and the UV Xform. i even tried the UV Map modifier as u suggested. And you're right I could just flip the texture backwards in 3Ds this way it comes out correctly when I load it, but I would really like to get to the source of this. Not sure what other problems I may run into down the line. But I just find it weird that complex objects come out correctly while standard primitives like cubes and spheres come out like this. I think that may play some kind of role in this.

##### Share on other sites

Satanir, I guess u you were right, feel like a dunce now.

After a little reading I found all I had to do was switch the position Y and position Z of the verts like so:

FbxVector4 position = fbxMesh->GetControlPointAt(controlPointIndex);
vS.position = D3DXVECTOR3(position[0], position[2], position[1]);

FbxVector2 tex;
bool isMapped;
fbxMesh->GetPolygonVertexUV(p, v, lUVSetName, tex, isMapped);
vS.uv = D3DXVECTOR2(tex[0], -tex[1]);

FbxVector4 norm;
fbxMesh->GetPolygonVertexNormal(p, v, norm);
vS.normal = D3DXVECTOR3(-norm[0], -norm[2], -norm[1]);


Thanks for the help. Hopefully this will also help someone else with the same issue.

• 23
• 10
• 19
• 15
• 14
• ### Similar Content

• By chiffre
Introduction:
In general my questions pertain to the differences between floating- and fixed-point data. Additionally I would like to understand when it can be advantageous to prefer fixed-point representation over floating-point representation in the context of vertex data and how the hardware deals with the different data-types. I believe I should be able to reduce the amount of data (bytes) necessary per vertex by choosing the most opportune representations for my vertex attributes. Thanks ahead of time if you, the reader, are considering the effort of reading this and helping me.
I found an old topic that shows this is possible in principal, but I am not sure I understand what the pitfalls are when using fixed-point representation and whether there are any hardware-based performance advantages/disadvantages.
(TLDR at bottom)
The Actual Post:
To my understanding HLSL/D3D11 offers not just the traditional floating point model in half-,single-, and double-precision, but also the fixed-point model in form of signed/unsigned normalized integers in 8-,10-,16-,24-, and 32-bit variants. Both models offer a finite sequence of "grid-points". The obvious difference between the two models is that the fixed-point model offers a constant spacing between values in the normalized range of [0,1] or [-1,1], while the floating point model allows for smaller "deltas" as you get closer to 0, and larger "deltas" the further you are away from 0.
To add some context, let me define a struct as an example:
struct VertexData { float[3] position; //3x32-bits float[2] texCoord; //2x32-bits float[3] normals; //3x32-bits } //Total of 32 bytes Every vertex gets a position, a coordinate on my texture, and a normal to do some light calculations. In this case we have 8x32=256bits per vertex. Since the texture coordinates lie in the interval [0,1] and the normal vector components are in the interval [-1,1] it would seem useful to use normalized representation as suggested in the topic linked at the top of the post. The texture coordinates might as well be represented in a fixed-point model, because it seems most useful to be able to sample the texture in a uniform manner, as the pixels don't get any "denser" as we get closer to 0. In other words the "delta" does not need to become any smaller as the texture coordinates approach (0,0). A similar argument can be made for the normal-vector, as a normal vector should be normalized anyway, and we want as many points as possible on the sphere around (0,0,0) with a radius of 1, and we don't care about precision around the origin. Even if we have large textures such as 4k by 4k (or the maximum allowed by D3D11, 16k by 16k) we only need as many grid-points on one axis, as there are pixels on one axis. An unsigned normalized 14 bit integer would be ideal, but because it is both unsupported and impractical, we will stick to an unsigned normalized 16 bit integer. The same type should take care of the normal vector coordinates, and might even be a bit overkill.
struct VertexData { float[3] position; //3x32-bits uint16_t[2] texCoord; //2x16bits uint16_t[3] normals; //3x16bits } //Total of 22 bytes Seems like a good start, and we might even be able to take it further, but before we pursue that path, here is my first question: can the GPU even work with the data in this format, or is all I have accomplished minimizing CPU-side RAM usage? Does the GPU have to convert the texture coordinates back to a floating-point model when I hand them over to the sampler in my pixel shader? I have looked up the data types for HLSL and I am not sure I even comprehend how to declare the vertex input type in HLSL. Would the following work?
struct VertexInputType { float3 pos; //this one is obvious unorm half2 tex; //half corresponds to a 16-bit float, so I assume this is wrong, but this the only 16-bit type I found on the linked MSDN site snorm half3 normal; //same as above } I assume this is possible somehow, as I have found input element formats such as: DXGI_FORMAT_R16G16B16A16_SNORM and DXGI_FORMAT_R16G16B16A16_UNORM (also available with a different number of components, as well as different component lengths). I might have to avoid 3-component vectors because there is no 3-component 16-bit input element format, but that is the least of my worries. The next question would be: what happens with my normals if I try to do lighting calculations with them in such a normalized-fixed-point format? Is there no issue as long as I take care not to mix floating- and fixed-point data? Or would that work as well? In general this gives rise to the question: how does the GPU handle fixed-point arithmetic? Is it the same as integer-arithmetic, and/or is it faster/slower than floating-point arithmetic?
Assuming that we still have a valid and useful VertexData format, how far could I take this while remaining on the sensible side of what could be called optimization? Theoretically I could use the an input element format such as DXGI_FORMAT_R10G10B10A2_UNORM to pack my normal coordinates into a 10-bit fixed-point format, and my verticies (in object space) might even be representable in a 16-bit unsigned normalized fixed-point format. That way I could end up with something like the following struct:
struct VertexData { uint16_t[3] pos; //3x16bits uint16_t[2] texCoord; //2x16bits uint32_t packedNormals; //10+10+10+2bits } //Total of 14 bytes Could I use a vertex structure like this without too much performance-loss on the GPU-side? If the GPU has to execute some sort of unpacking algorithm in the background I might as well let it be. In the end I have a functioning deferred renderer, but I would like to reduce the memory footprint of the huge amount of vertecies involved in rendering my landscape.
TLDR: I have a lot of vertices that I need to render and I want to reduce the RAM-usage without introducing crazy compression/decompression algorithms to the CPU or GPU. I am hoping to find a solution by involving fixed-point data-types, but I am not exactly sure how how that would work.
• By cozzie
Hi all,
I was wondering it it matters in which order you draw 2D and 3D items, looking at the BeginDraw/EndDraw calls on a D2D rendertarget.
The order in which you do the actual draw calls is clear, 3D first then 2D, means the 2D (DrawText in this case) is in front of the 3D scene.
The question is mainly about when to call the BeginDraw and EndDraw.
Note that I'm drawing D2D stuff through a DXGI surface linked to the 3D RT.
Option 1:
A - Begin frame, clear D3D RT
B - Draw 3D
C - BeginDraw D2D RT
D - Draw 2D
E - EndDraw D2D RT
F - Present
Option 2:
A - Begin frame, clear D3D RT + BeginDraw D2D RT
B - Draw 3D
C - Draw 2D
D - EndDraw D2D RT
E- Present
Would there be a difference (performance/issue?) in using option 2? (versus 1)
Any input is appreciated.

• Do you know any papers that cover custom data structures like lists or binary trees implemented in hlsl without CUDA that work perfectly fine no matter how many threads try to use them at any given time?
• By cozzie
Hi all,
Last week I noticed that when I run my test application(s) in Renderdoc, it crashes when it enable my code that uses D2D/DirectWrite. In Visual Studio no issues occur (debug or release), but when I run the same executable in Renderdoc, it crashes somehow (assert of D2D rendertarget or without any information). Before I spend hours on debugging/ figuring it out, does someone have experience with this symptom and/or know if Renderdoc has known issues with D2D? (if so, that would be bad news for debugging my application in the future );
I can also post some more information on what happens, code and which code commented out, eliminates the problems (when running in RenderDoc).
Any input is appreciated.

• Hi Guys,
I understand how to create input layouts etc... But I am wondering is it at all possible to derive an input layout from a shader and create the input layout directly from this? (Rather than manually specifying the input layout format?)