Sign in to follow this  
knobby67

OpenGL md5 vanishing textures

Recommended Posts

Hi all, I hope some one can help me out with this, I've just started working on loading MD5 models, all was going well until I tried to load textures, I've "flipped" the co-ordinates so they map on opengl co-ordinates. However when I run the animation parts of the texture keeps vanishing, so about 50% look right, 40% disappear/reappear as the animation runs, 10% flicker. I've got the co-ordiantes from the model which i've ran on a view and they work on that exe. I'm only loading in one texture, the diffuse map, but that shouldn't make any difference. Do I need to recalculate texture coordinates, like the meshes? Has anyone else experienced this, if so can you advise? Thanks.

Share this post


Link to post
Share on other sites
I played with md5 model loading not so long ago - how exactly do you load your texture coordinates - they should be directly loaded and used (I've seen no deformations of texture coordinates so far) and of course flipped in Y axis.
Aren't you computing them on run using weights (which is incorrect - but it might cause deformations)?
Or don't you have wrong animation (because coordinate moves with vertex)?

Share this post


Link to post
Share on other sites
Hi no I don't transform the texture coordinates on the fly. I just load them from the file.

However I do change the x,y,z of the vertexes so the correspond to the coordinate system of opengl (eg move y is up ect), I then flip the textures so they are look right, eg head texture maps onto head.

However I have found the vertext "flips" are slightly different to these I use on 3ds and AES models I flip these by

Vx=Vx
Vy=Vz
Vz=-Vy

with md5 I do

Vx=Vy
Vy=Vz
Vz=Vx

This "looks" right but perhaps is wrong?



Share this post


Link to post
Share on other sites
#EmmeKappaErre - this would cause wrong visiblity of texture even while not animating, and it'd probably do this with the texture even before starting the animation (anyway as I think from what I've read this is not a problem)

Although you're right - one should always use clamped coordinates (if it's not your intention to use unclamped onex).

#knobby67 - Yeah, this is common thing - that one with swapping vertices while loading. The axis stuff is probably causing the problems - let me post you some pseudo code of mine (lets say I've loaded the verts, weights and coords, quaternions, etc. as they are ... this code is very unoptimised, just to show off how do the stuff most simple way - you can try then some GPU skinning, etc. but It's complicated and not good for "showing the way"):
// first I need to transform all the joints:
// For every joint
for(int i = 0; i < numberOfJoints; i++)
{
// Get it's ID
md5.animations[animationNo].joints[i].id = i;
// and parent ID
md5.animations[animationNo].joints[i].parent = md5.animations[animationNo].parent[i];

// If it has no parent
if(md5.animations[animationNo].parent[i] == -1)
{
// Set it's position and quaternion as the position and quaternion defined for current frame of animation
md5.animations[animationNo].joints[i].pos = md5.animations[animationNo].frames[currentFrame].joints[i].position;
md5.animations[animationNo].joints[i].quat = md5.animations[animationNo].frames[currentFrame].joints[i].quaternion;
}
// Otherwise it has some parent
else
{
// Get me position and quaternion of current joint from current frame of animation, though it needs to be transformed
// by parent joint (because it's in some kind of HIERARCHY)
tVector3 thisPosition = md5.animations[animationNo].frames[currentFrame].joints[i].position;
md5_quaternion thisQuaternion = md5.animations[animationNo].frames[currentFrame].joints[i].quaternion;

// Get me current joints parent joint into "parent" variable
md5_joint parent = md5.animations[animationNo].joints[md5.animations[animationNo].parent[i]];

// Now lets compute some rotation
// First we need to rotate current joint by its parent joint rotation (e.g. rotate it with all hierarchy prior to it)
tVector3 rotatedPos;
rotatedPos = RotatePointAroundQuaternion(parent.quaternion, thisPosition);
// And now comes position computing - simply use position after rotating and add parents position (transforming it to
// right place - where the joint should be)
md5.animations[animationNo].joints[i].position.x = rotatedPos.x + parent.position.x;
md5.animations[animationNo].joints[i].position.y = rotatedPos.y + parent.position.y;
md5.animations[animationNo].joints[i].position.z = rotatedPos.z + parent.position.z;

// And at last some quaternion math - joints current quaternion must be computed as multiplication of its and the
// parents quaternion, of course normalized (for importance of this and why this is important see some quaternion
// math book)
md5.animations[animationNo].joints[i].quaternion = MultiplyQuaternions(parent.quaternion, thisQuaternion);
md5.animations[animationNo].joints[i].quaternion = NormalizeQuaternion(md5.animations[animationNumber].joints[i].quaternion);
}
}

// Now I need to compute right positions (I'm showing just computing position of first vertex in triangle, the other two are the same (except you need to use different vertex indicies)
// Lets do it the simple way ... legacy glBegin/glEnd forever :D ... just joking, almost everyone is using VBOs and so,
// so it's just to show it the simpliest way possible.
glBegin(GL_TRIANGLES);
// Cycling cycling - for every mesh and every triangle in it (showing just first vertex in triangle)
for(int i = 0; i < md5.numMeshes; i++)
{
for(int j = 0; j < md5.meshes[i].numTri; j++)
{
// Texture coordinates 1.0f - coordinateY isn't necessary, even -coordinateY will work, but to be sure about
// clamping stuff
glTexCoord2f(md5.meshes[i].vert[md5.meshes[i].tri[j].a].texCoord.x,
1.0f - md5.meshes[i].vert[md5.meshes[i].tri[j].a].texCoord.y);
// tVector3 is some kind of structure that holds 3 floats - X Y and Z
tVector3 finalVert;
// Initialize it (I init is defaultly as this, but to show it needs to equal (0,0,0)
finalVert = tVector3(0.0f, 0.0f, 0.0f);
// now lets sum the weights to get correct position
for(int k = md5.meshes[i].vert[md5.meshes[i].tri[j].a].weightBegin; k < md5.meshes[i].vert[md5.meshes[i].tri[j].a].weightBegin + md5.meshes[i].vert[md5.meshes[i].tri[j].a].weightNum; k++)
{
// Gimme weight and joint for this weight
md5_weight weight = md5.meshes[i].weight[k];
md5_joint joint = md5.animations[animationNumber].thisFrame.joints[weight.jointId];

// And now some stuff with rotation (weight needs to be rotated around joints quaternion)
tVector3 temp = tVector3(0.0f, 0.0f, 0.0f);
temp = RotatePoint(joint.quat, weight.pos);

// And finally add it's position to vertex (based upon the weight "effect" on it
finalVert.x += (joint.pos.x + temp.x) * weight.weightStrength;
finalVert.y += (joint.pos.y + temp.y) * weight.weightStrength;
finalVert.z += (joint.pos.z + temp.z) * weight.weightStrength;
}
// The sum of all that weight computing into finalVert gives us correct position of vertex, and just right now you flip
// X Y Z into X Z-Y ... that's all
glVertex3f(finalVert.x, finalVert.z,-finalVert.y);

// Now you need to do the same for other two vertices of triangle
}
}
// And thy mighty procedure to complete this code-show and fulfill the purpose of my life :D
glEnd();






I appologize for long post

Share this post


Link to post
Share on other sites
Thanks for the help everyone, and thanks for the code example, but I think that's basically what I'm doing? Except I change my texture when I load using
the texture matrix

glMatrixMode (GL_TEXTURE);
glLoadIdentity ();
glScalef (1.0f, -1.0f, 1.0f);
glTranslatef (0.0f, -1.0f, 0.0f);
glMatrixMode (GL_MODELVIEW);


Should I not do this and "flip" the coordinates on the fly?

Also one other thing, I see in your example code you "flip" vertex like me for ASE 3DS model, Vx=Vx,Vy=Vz, Vy=-Vy, but on the two sample MD5's I could fine
I've had to do Vx=Vy, Vy=Vz, Vz=Vx. Can you confirm that you do the first way, in which case it seems there's something else wrong with my code (even though it "looks" right, without textures :s ). Thanks

Share this post


Link to post
Share on other sites
I tried the texture matrix code you're posting and it's not what is causing the problems (anyway you should rather do loading texture coordinates and flipping them while loading - because these texture matrix operations must be done every frame (as long as you're using more than 1 model), but precomputing while loading not).

About that X Z-Y and Y Z X, you just mirror the model into some direction (so this won't cause issues). Although you have to use flipped axes at last (when you call glVertex, or as you generate vertex buffers - for joint position computing and for vertex position computing you have to use X Y Z - otherwise you can have sometimes X Y Z and sometimes X Z Y, etc. - and this will cause issues in vertex and its information transform).

So in final it really seems there is something more strange in the code...

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Announcements

  • Forum Statistics

    • Total Topics
      628370
    • Total Posts
      2982300
  • Similar Content

    • By test opty
      Hi all,
       
      I'm starting OpenGL using a tut on the Web. But at this point I would like to know the primitives needed for creating a window using OpenGL. So on Windows and using MS VS 2017, what is the simplest code required to render a window with the title of "First Rectangle", please?
       
       
    • By DejayHextrix
      Hi, New here. 
      I need some help. My fiance and I like to play this mobile game online that goes by real time. Her and I are always working but when we have free time we like to play this game. We don't always got time throughout the day to Queue Buildings, troops, Upgrades....etc.... 
      I was told to look into DLL Injection and OpenGL/DirectX Hooking. Is this true? Is this what I need to learn? 
      How do I read the Android files, or modify the files, or get the in-game tags/variables for the game I want? 
      Any assistance on this would be most appreciated. I been everywhere and seems no one knows or is to lazy to help me out. It would be nice to have assistance for once. I don't know what I need to learn. 
      So links of topics I need to learn within the comment section would be SOOOOO.....Helpful. Anything to just get me started. 
      Thanks, 
      Dejay Hextrix 
    • By mellinoe
      Hi all,
      First time poster here, although I've been reading posts here for quite a while. This place has been invaluable for learning graphics programming -- thanks for a great resource!
      Right now, I'm working on a graphics abstraction layer for .NET which supports D3D11, Vulkan, and OpenGL at the moment. I have implemented most of my planned features already, and things are working well. Some remaining features that I am planning are Compute Shaders, and some flavor of read-write shader resources. At the moment, my shaders can just get simple read-only access to a uniform (or constant) buffer, a texture, or a sampler. Unfortunately, I'm having a tough time grasping the distinctions between all of the different kinds of read-write resources that are available. In D3D alone, there seem to be 5 or 6 different kinds of resources with similar but different characteristics. On top of that, I get the impression that some of them are more or less "obsoleted" by the newer kinds, and don't have much of a place in modern code. There seem to be a few pivots:
      The data source/destination (buffer or texture) Read-write or read-only Structured or unstructured (?) Ordered vs unordered (?) These are just my observations based on a lot of MSDN and OpenGL doc reading. For my library, I'm not interested in exposing every possibility to the user -- just trying to find a good "middle-ground" that can be represented cleanly across API's which is good enough for common scenarios.
      Can anyone give a sort of "overview" of the different options, and perhaps compare/contrast the concepts between Direct3D, OpenGL, and Vulkan? I'd also be very interested in hearing how other folks have abstracted these concepts in their libraries.
    • By aejt
      I recently started getting into graphics programming (2nd try, first try was many years ago) and I'm working on a 3d rendering engine which I hope to be able to make a 3D game with sooner or later. I have plenty of C++ experience, but not a lot when it comes to graphics, and while it's definitely going much better this time, I'm having trouble figuring out how assets are usually handled by engines.
      I'm not having trouble with handling the GPU resources, but more so with how the resources should be defined and used in the system (materials, models, etc).
      This is my plan now, I've implemented most of it except for the XML parts and factories and those are the ones I'm not sure of at all:
      I have these classes:
      For GPU resources:
      Geometry: holds and manages everything needed to render a geometry: VAO, VBO, EBO. Texture: holds and manages a texture which is loaded into the GPU. Shader: holds and manages a shader which is loaded into the GPU. For assets relying on GPU resources:
      Material: holds a shader resource, multiple texture resources, as well as uniform settings. Mesh: holds a geometry and a material. Model: holds multiple meshes, possibly in a tree structure to more easily support skinning later on? For handling GPU resources:
      ResourceCache<T>: T can be any resource loaded into the GPU. It owns these resources and only hands out handles to them on request (currently string identifiers are used when requesting handles, but all resources are stored in a vector and each handle only contains resource's index in that vector) Resource<T>: The handles given out from ResourceCache. The handles are reference counted and to get the underlying resource you simply deference like with pointers (*handle).  
      And my plan is to define everything into these XML documents to abstract away files:
      Resources.xml for ref-counted GPU resources (geometry, shaders, textures) Resources are assigned names/ids and resource files, and possibly some attributes (what vertex attributes does this geometry have? what vertex attributes does this shader expect? what uniforms does this shader use? and so on) Are reference counted using ResourceCache<T> Assets.xml for assets using the GPU resources (materials, meshes, models) Assets are not reference counted, but they hold handles to ref-counted resources. References the resources defined in Resources.xml by names/ids. The XMLs are loaded into some structure in memory which is then used for loading the resources/assets using factory classes:
      Factory classes for resources:
      For example, a texture factory could contain the texture definitions from the XML containing data about textures in the game, as well as a cache containing all loaded textures. This means it has mappings from each name/id to a file and when asked to load a texture with a name/id, it can look up its path and use a "BinaryLoader" to either load the file and create the resource directly, or asynchronously load the file's data into a queue which then can be read from later to create the resources synchronously in the GL context. These factories only return handles.
      Factory classes for assets:
      Much like for resources, these classes contain the definitions for the assets they can load. For example, with the definition the MaterialFactory will know which shader, textures and possibly uniform a certain material has, and with the help of TextureFactory and ShaderFactory, it can retrieve handles to the resources it needs (Shader + Textures), setup itself from XML data (uniform values), and return a created instance of requested material. These factories return actual instances, not handles (but the instances contain handles).
       
       
      Is this a good or commonly used approach? Is this going to bite me in the ass later on? Are there other more preferable approaches? Is this outside of the scope of a 3d renderer and should be on the engine side? I'd love to receive and kind of advice or suggestions!
      Thanks!
    • By nedondev
      I 'm learning how to create game by using opengl with c/c++ coding, so here is my fist game. In video description also have game contain in Dropbox. May be I will make it better in future.
      Thanks.
  • Popular Now