Making Of 'HEMTT-M1075'
Gurmukh Bhasin takes us through the process of modeling and rendering his real world military vehicle using Maya, mental ray and Photoshop.
In this making of I will describe the steps I took to accurately model and detail, at real world scale, a HEMTT-M1075 military cargo truck. I will also take you through my process of photorealistic rendering with mental ray using the Physical Sun and Sky lighting and compositing the render passes in Photoshop.
To start a project like this, or any project for that matter, it is always a good idea to collect lots of image references. You can never have enough of these! The most important things to look for can be broken down into three different categories: Orthographic views, three-quarter overall views, and detail views. I like to use the-blueprints and blueprintbox to find drawings. For the three-quarter overall views and detail views, the best website I found for amazing photo references of military vehicles is primeportal. They have high-resolution walk-arounds of virtually any military vehicle available.
Step 1: Blocking in the base model
As you would with a quick sketch, I blocked in the vehicle with as little detail as possible. At this stage it was very important that I put everything in the right place and got the right proportions of the vehicle before spending too much time creating details.
Step 2: Start modeling the detail
I like to model as if I were building this vehicle in the real world. It might have something to do with my background as an architect, but I always start by modeling the frame and undercarriage first.
This part was the most complex part to construct as it was the hardest part to find reference photos for. Most of it was modeled as accurately as I could figure out on my own from the photos I could find. It is important to consider that most of these details are hidden, and primarily serve to fill the gaps in the truck model. I find it important to have as many of these hidden details as possible as it really fills the gaps and gives off the feeling of this being a real vehicle and not a hollow 3D model.
Tip: Model all your parts as simply as possible. Start with primitive shapes and build up from there. Insert edge loops where you want your model to have sharp edges and toggle between the smooth mesh preview by hitting 1 and 3 on your keyboard to check and see how your model is coming along.
Step 3: Continuing to model the detail
I then continued modeling the more complex parts (the back and wheels). I typically save the front of the model for last as I know it is the part I will need the least amount of time figuring out how to model.
Tip 2: For personal projects I like to post my progress on various social media outlets to get feedback from peers and even mentors. It gets you pumped to keep going when your friends compliment your work and someone can point out mistakes or things that don't look right which you may have missed.
Tip 3: Check your model by applying a Blinn material to the entire thing from time to time. This allows you to check for wobbles in the surface and see if you have a vertex pulled in the wrong direction. Also create occlusion renders throughout your progress, to make sure things are looking good and to check to see if your parts are all relating on the same scale and look right together.
Step 4: Finish the modeling
Finally, I finished modeling the front of the vehicle. All parts of the vehicle were modeled to be as accurate as possible according to the photo references I have collected.
It is important to model your vehicle to scale, in real world units, so you can make sure you are modeling things accurately and to the correct proportions. For example, you know a footstep is about 6" long or you can go out and measure a windshield wiper on a semi truck to make sure you are modeling your windows at the right size. You can then figure out the size of uncommon parts by measuring against the familiar parts and comparing them in your reference photos.
These images show the occlusion and wireframe renders of the entire vehicle
Step 5: Creating Materials
At this stage, I started applying basic materials to my model. I didn't want to UV this vehicle as I had already spent a lot of time completing the model, so I decided I would texture my vehicle in 2D in Photoshop as a part of the final render composite.
To create the materials, I used the mental ray mia_material_x materials. If you click on presets you can choose from a list of different material options that you can adjust to your personal preferences. For example, choose the glass preset for the windows or rubber for the tires, etc…
Step 6: Lighting
For the lighting setup, I usually just use the Physical Sun and Sky in mental ray. It's really simple to use and gives a subtle, but realistic, feel to your renders. I like to add 1 Secondary Diffuse Bounce to Final Gather to give the lighting a little more color bounce in the render.
I rendered out the final passes with a linear workflow, which is a bit complicated to set up, but it really gives a vivid, photorealistic quality to your renders. I suggest looking up how to do this in mental ray if you are interested in creating photorealistic renders with the mia_material_x materials. I followed a step by step tutorial on how to set this up properly, and you can find how to do this by doing a basic internet search for 'rendering with a linear workflow Maya.'
Step 7: Render layers
For my render layers I created a few simple passes that I would later composite in Photoshop. I made a beauty pass, a dust pass, a metal/rust pass, an occlusion pass and material ID passes.
The beauty pass
The beauty pass is the overall color and base materials of the vehicle. This pass will be the base upon which you will layer everything on top of.
The dust pass
The dust pass is made by adding a dust material to every part of the vehicle. This pass will be masked out completely and you can paint into the mask to reveal the dust where you want it to show in the final composite.
The metal/rust pass
The metal/rust pass is the same, but only added to the metal parts of the vehicle. This pass will also be masked out and painted into the mask to reveal where you want the metal and rust to be shown.
The occlusion pass
The occlusion pass is put on top of all the layers and changed to multiply to help define where the ambient shadows are in the render.
The material ID passes
The material ID passes are used for quick selection of different materials for use in Photoshop. I like to use only red, green and blue colors in my material ID passes as this gives me automatic channel selections in the RGB in Photoshop and makes for quicker selections.
Step 8: The background image and importing the model
After all of your render passes are completed it is time to combine them in Photoshop. I started off by searching for a background image to place my vehicle in. My background image was from Wikipedia (and is under the Creative Commons Attribution-Share Alike 3.0 Unported license).
Next, I adjusted the image a little, moving mountains around and adding a few more mountains to the background to make it a little more interesting to look at and fit in the scene better with the truck.
Then I brought in the base render of the truck over the background image and placed it where I wanted it to fit in the scene. I created the dirt road for the vehicle by masking out the parts of the rendered ground which I didn't want to show and overlaying a gravel texture on the ground to give it detail.
Here you will see my final adjusted background image and model
Step 9: Adding the passes
I then added the dust pass and metal/rust pass over the top and fully masked out the layers so I could paint into the masks to reveal the dirt, metal and rust where I wanted it to show. I like to use dirt and grunge brushes for this and stamp in where the dust and metal/rust will show.
These images show an example of painting in the mask to reveal the dust and the final dust pass and metal/rust passes on the vehicle
Step 10: Final touches
Once all the dust and metal/rust is revealed and I am happy with it, I painted some flying dust clouds over the scene using a cloud brush. The last step is to do some layer adjustments. I did a hue and saturation adjustment to play with the colors; a brightness and contrast adjustment to make the brights and darks stand out a little more; and I always like to put a photo filter over everything to make sure all the different renders and photos used share a similar color tint and feel like they belong together.
Tip 4: When rendering in mental ray with the Physical Sun and Sky you get a base image with a sky background. The colors of the sky leave a slight tint on everything in your render as does the sky in the real world. If you want to add a different sky to your final image it is important to adjust your render to match the color of the sky in the photo, as the sky color drives all the other colors in your scene. One of the biggest things that make an image look too CG is if the sky doesn't match the renders.