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How should I add 3D animation in my game?

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#1 tom_mai78101   Members   -  Reputation: 580


Posted 15 April 2013 - 12:54 PM

I have created a simple 3D animation, which is a cube that is bobbing its head back and forth, and using Blender to export the animation into 3DS Max file format.




According to this link here, I have satisfied the first and second requirements, which are to use a file format (3DS Max file) that is saved as a binary file, and to create a 3DS file loader.


From here on, I couldn't follow the instructions. The respondent said to skin the weighted mesh by going through the vertex shader, does it mean I have to use GLSL to do animation by controlling the vertex and calculate the weight on the mesh? I even got more confused with the part that says to use the matrices that were included with the skins. But it got me thinking that maybe 3DS Max files have a file structure hierarchy that stores data useful for these.


I went to this site that teaches how to create a 3DS Max loader. There, it includes the following hierarchical file structure known.


      OBJECT BLOCK 0x4000
         TRIANGULAR MESH 0x4100
            VERTICES LIST 0x4110
            FACES DESCRIPTION 0x4120
               FACES MATERIAL 0x4130
               SMOOTHING GROUP LIST 0x4150
         LIGHT 0x4600
            SPOTLIGHT 0x4610
         CAMERA 0x4700
         MATERIAL NAME 0xA000
         AMBIENT COLOR 0xA010
         DIFFUSE COLOR 0xA020
         SPECULAR COLOR 0xA030
         TEXTURE MAP 1 0xA200
         BUMP MAP 0xA230
         REFLECTION MAP 0xA220
            MAPPING FILENAME 0xA300
            MAPPING PARAMETERS 0xA351
         FRAMES (START AND END) 0xB008
            OBJECT NAME 0xB010
            OBJECT PIVOT POINT 0xB013
            POSITION TRACK 0xB020
            ROTATION TRACK 0xB021
            SCALE TRACK 0xB022
            HIERARCHY POSITION 0xB030


I saw that there is a chunk that store animation frames, which are probably keyframes that appears in Blender's Dopesheet. But the file structure didn't tell me where I can load (or read) matrices that is used to calculate the vertices when the animation is being played. Thus, I'm stucked.


1. What does the third requirement meant for me to do?

2. Are there examples / sample codes that loads 3DS Max files and animate the models in the program?

3. What else should I need to learn more about?

4. In GLSL, what parts should I learn more about when it comes to animation?


Thanks in advance.

Edited by tom_mai78101, 15 April 2013 - 12:54 PM.


#2 tom_mai78101   Members   -  Reputation: 580


Posted 15 April 2013 - 04:11 PM

I'm looking for the core basics of obtaining keyframes, how to use keyframes, obtaining data that does the animation calculations, and how to handle those data. If the information is available, where can I read more into these? Google searching doesn't seem to work for me. The art of Googling has not been passed down upon me.

#3 EarthBanana   Members   -  Reputation: 1044


Posted 16 April 2013 - 11:26 AM

Have you looked at assimp? http://assimp.sourceforge.net/


You can see how to use it here http://ogldev.atspace.co.uk/www/tutorial38/tutorial38.html

#4 L. Spiro   Crossbones+   -  Reputation: 15392


Posted 16 April 2013 - 04:46 PM

Firstly, I would recommend using FBX for one very powerful reason: It can evaluate the scene at any time during animations.


One of the major problems is that keyframes can be of various types and each type can have multiple flags or parameters.

For example, between 2 keyframes, Catmull-Rom interpolation could be used or it could be linear interpolation.  Or there could be no interpolation and instead the value of either first or second keyframe is used for the whole duration between them.


Evaluating all of this at run-time is quite expensive.  Your run-time should only be doing the cheapest and fastest interpolation, which is linear interpolation.

That means your animation converter should add as many keyframes as it takes so that linearly interpolating between them gets you as close to the original animation as possible.

That means it would be extremely helpful if you used an SDK that can evaluate the animations for you so all you have to do is call their functions and added fake keyframes to your own data.


The FBX SDK is the only SDK that allows you to do this.  It will use the proper interpolation type between keyframes and give you back the value at the given time on the given track.  Extremely handy.



How to store this data is entirely up to you.  You write your own exporter and importers.

Once you have the data inside your game you need to search Google for “GLSL Skinning”.

You should add another vec4 to your vertex buffers for the weights of 4 matrices and a 32-bit int for the 4 matrix indices.

You will find many tutorials on this online.



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