Friday, 27 November 2015

Shotgun 3d model

Shotgun Pump Action

Here is my new Pump Action Shotgun model available from Turbosquid now. You can get it for Maya, Max, in fbx, or obj format. It's a polygonal model coming in at  faces 7519  verts 7485 for the shotgun with three cartridge models included. If you go over to turbosquid you can see a little animation of the shotgun pump action firing and ejecting shells.

I'm going to talk here a little about how I built the model and converting it from Maya to Max.
Shotgun base mesh in Maya
Maya Low poly shotgun
 I started out with a low poly base mesh which I built in Maya I then UV mapped the low poly model. I decided to have a look around to see if I could find a better UV mapping solution for this model. I normally make organic models and have been using Zbrushes UV master but it's no good for mechanical stuff like the shotgun. I ended up using Roadkill, it's a good program for low polygon. I also tried Maya's unfold but found it to be so loaded with bugs that it was unworkable.

Roadkill shotgun UV mapped showing UV islands
Shotgun in Roadkill for UV mapping

Once this was done I exported the model as an obj and brought it into Zbrush for detailing. I separated the model into a number of subtools so that I could get a higher level of detail into the model.

Base model in Zbrush
Below are my high poly Zbrush sculpts with a shiny material on them so they look pretty. I found it quite hard to sculpt a mechanical object like this, but the idea was to push myself specifically into a hard surface object and I learnt a lot from it.

The next step for me was to get normal maps from the high poly sculpt onto a lower poly version of the shotgun. For this step I used xNormal which I have been using for a while and for me it seems the most reliable tool for this. As I had a number of subtools and because some areas of the shotgun overlap I used my subtools to normal map the shotgun in sections that fit into one texture page when assembled (if you look at the Roadkill screen shot you can see my texture page). Overlapping objects in normal mapping will cause errors if not dealt with separately.

This is where things went wrong..................
I had some ugly texture stretching going on which you can see above. The strange saw tooth effect showing on the piece above is pixelation on a normal map. What I did to fix this was re-map the shotgun at a higher poly division and also I altered my UV islands. I also rebuilt the barrel and used edge creasing in Zbrush to keep my edges sharp. The rifle butt needed re sculpting as I didn't have enough geometry in my low poly to make my original version work. All useful things to learn, edge creasing in Zbrush is an easy way to keep your crisp edges. For mechanical objects it's better to be generous with your low poly when it comes to curved areas like the rifle barrel. I discovered that Roadkill does not cope with higher poly models and ended up mapping the shotgun in sections, it wasn't too bad, I used the subtool division from Zbrush.

Next step texturng. Above is an early base colour version. You can see the barrel has changed from the Zbrush version. Below is the altered mapping from the higher poly division shotgun.

One more thing I wanted to share, as it drove me up the wall. This is the first model that I have converted to Max. It's pretty simple for a model like this which is just geometry with some separate parts. I exported the model as an obj. I learnt that to keep my pivot points accurate I needed to export all elements from the origin. I learnt how to rebuild my materials in Max, all pretty straight forward........until normal map seams!

The horror!

I'm going to run through what happened and how I solved it starting with setting up the normal map slot in the material. The first step is to go to the maps section of the material. Set the bump map amount to 100, default is 30. Next click the map button marked none, select "Normal Bump" from the Material/Map Browser. Now select the normal texture node.
Normal Map set up in Max help images for setting up your normal map texture file
Select the Normal slot marked none and pick bitmap from the Material/Map Browser. Lastly and here is the fix. Once you have navigated to your normal map texture file go to the gamma option, select override and set it to 1 as shown in the image below. The problem is due to Max's default gamma option being set to 2 which gives you your seams.
Max gamma fix for normal map seams which options to use
I had to do lots of googeling to get to the bottom of that one, so I hope this will help others with there normal map woes. Typical Max that the default value doesn't work.
I could also tell you a thing or three about shotgun calibre, imperial to metric but I think it might be too exciting for you (sarcasm).

Shotgun pump actionShotgun Wireframe


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