Celestia Forums

I just got an email from one of my friends that lets me use his models.

Tim, I like to know:
What is the ideal number of polygons for Celestia?
This information will be useful for me when I create new meshes.

I wasn't really sure how to answer him.
So I answered him with an assumtion-"I don't really think it's the number of polygons so much as it's the number and size of the textures used."

Does this sound like the correct assumtion to make?
I have never seen anything mentioned about polygon count in meshes used for Celestia.

Thanks,
Tim

I think your friend is asking for the polygons' limitation-per-mesh in a hierarchical tree model, like the .3DS format has, which is 65k. This format can be composed by several meshes, each one of 65k polygons max. Virtually, there is no polygons' limit for meshes made in CMOD format. If the CMOD is got through 3DS' conversion, the original .3DS models must follows the rule above; instead, if the CMOD is got through .OBJ, each one mesh can have the same number of polygons of the original .OBJ, no matter of how many polygons.

Notice a thing, though. If the 3D modeler of your friend is Blender or Anim8tor as well, there are file exporters for the CMOD format which avoids the conversions above, and one can operate upon the 3D model by saving the work into their proprietary file formats (which broken the 65k 3DS' limit, of course) for then to export it directly in CMOD.

Well I know he uses Lightwave.
Then I convert them to 3ds, do my tweaking, then export to cmod using Anim8or.
I will ask him to be more specific as to what his meaning is.

Thanks,
Tim

fungun wrote:Well I know he uses Lightwave.
Then I convert them to 3ds, do my tweaking, then export to cmod using Anim8or.
I will ask him to be more specific as to what his meaning is.

Thanks,
Tim

Yup! I like Lightwave. But if you are using Anim8or for the CMOD conversion, maybe isn't necessary to convert the model in .3DS, since Anim8tor can import the Lightwave objects (.LWO). Perhaps is such a concern that your friend was asking for? That is, to know whether the CMOD would have polygons' limitations in order to avoid problems during the direct LWO > CMOD conversion with Anim8or when the former were made of meshes with much more polygons than 65k each one, without the LWO > 3DS conversion as intermediate step.

But if you are using Anim8or for the CMOD conversion, maybe isn't necessary to convert the model in .3DS, since Anim8tor can import the Lightwave objects (.LWO).

The only problem with doing it straight from the .lwo file, is that 99.9% of the time Anim8or complains about the obj file missing and the model won't load.
Right now I convert to 3ds, load it in Anim8or, reasign the textures, tweak the model and/or textures then export to cmod.
I am waiting for his next email, but in the mean time I "think" he maybe talking load times. His models are rather large and detailed.
The one I am working on now, the cmod is over 50 MB, and I'm not finished with it yet.

Thanks,
Tim

Although individual meshes (objects) are limited in size within 3DS model files, a 3DS model file can contain multiple meshes.

Testing done when CMOD was first developed indicated that CMOD models were drawn on the screen in about 2/3 the time it took Celestia to draw the 3DS versions of the same models (i.e. CMOD had 1.5x the framerate of 3DS). I don't think there's been any significant change since then.

Load time is going to be proportional to the file size, including both model and surface texture sizes. That's why many scripted addons preload models before they're actually viewed.

Large models are going to be slow no matter what you do. To get better runtime performance you can use lower resolution models with higher-resolution surface textures to make them look better than they are under the skin.