Designing Mechs in SketchUp: Part 2

Take SketchUp models to the next level with this KeyShot rendering guide for mechs...

In this tutorial, we will learn about how to complete a portfolio piece of a mech design in SketchUp, KeyShot and Photoshop. The previous part of the tutorial covered the process of designing the mech from thumbnail sketches to a finished 3D model.

In this next part, we will cover labeling the model's IDs, where we'll think about the distribution and proportions of the different materials. Then we'll move on to posing the model, and discuss how the camera angle would affect the pose. After that, we'll take the model to KeyShot to assign materials to the different parts. We'll touch on the basic interface and some important tools in KeyShot, and use KeyShot's label system to add not only decorative labels but also stains and weathering to the surfaces.

Finally, we'll use Photoshop to do the final touches, where we'll also briefly touch on using good composition and lighting to create an appealing scene, and some basic photo-compositing techniques.

Step 01: Labeling IDs and posing

The model is finished at this point, and it is time to label the IDs which will be used to assign materials later in KeyShot. At this point, I have a general idea of how I want to distribute different materials. Although I'm not sure yet what materials I will use, I know that I want a dominant material that takes up most of the space (dark green), a secondary material for color decoration (dark red), and a third material for creating 'breaks' and adding rhythm to the color distribution (bright green). For some small bits which I'm not yet sure about, I simply choose a new color for easy adjustment later. I also know where I will assign metal, such as the handles, hydraulics, and some parts covered by panels, so I use the same color (pink) for all the metal parts.

After labeling the IDs, I start to re-group parts in preparation for posing. I group the parts that will move together (fig.01b and fig.01c). However, I still edit within the biggest component, so all the re-grouping will be reflected to the other side.

Fig.1a - The model with IDs labeled ready for KeyShot

Fig.1b - Grouping parts that will move together on the front legs

Fig.1c - Grouping parts that will move together on the back legs

Step 02: Simple posing

Now I move to pose the mech. I explode the biggest mirrored components, so when I make changes to one side of the body, it won't affect the other side any more, but all the groups I created on both sides before will stay grouped, and I don't have to worry re-grouping them again.

As well as thinking about the biggest feature I want to show on this mech, another consideration when posing is how the camera angle will affect what can be seen and what can't. In this case, the camera angle I plan to have is a three-quarter view. Therefore, I pose the mech's right leg stretching out, and its left leg closer to the body, instead of the opposite. In that way, I can show as much of the design as possible. I also turn the 'head' part a little to the side, as if it's looking around.

Fig.2a - Don't forget to Explode the components so they're no longer mirrored

Fig.2b - Luckily, the groups on both sides of the body will stay grouped even after using Explode

Step 03: Adding a background

Since I plan to showcase an entire scene instead of just the mech design, I download props from the 3D Warehouse in SketchUp and set up a background for the scene. As I mentioned previously, I already have a rough idea that it's a small scout mech. I further develop that idea into a police patrol mech that is lightweight with great mobile ability, meant for searching instead of aggressively hunting down targets. This idea inspires me to have some fun and do a background that shows an almost propaganda image: a beautiful park scene to show how well-maintained the social order is in the area.

While placing props, I think about the composition of the scene: the foreground with some fences and tree leaves, the middle ground with the mech, and the far background with a bridge. I think about how to use the elements I can find in a park to create an interesting composition and believable environment, e.g. there shouldn't be fences in front of benches, and lamp-posts are very likely near a bench, as well as trash cans. I also use the road path, coming in from the left, as a guiding element to lead the eye to the mech, before the eye is stopped by the tree leaves in the upper-right corner.

Starting to add a background with SketchUp assets

Step 04: Cropping image

After I've finished everything in SketchUp, I export the scene as an OBJ file and bring it into KeyShot. The first thing I do is play around with the camera and decide which part of the image I want to include in the final render. The red box marked in the image indicates what will show in the final render. I can adjust the resolution ratio by going to Settings > Resolution Presets. Unless it's necessary, I don't recommend messing around with the original ratio; just make sure to check the Lock Resolution, so even if the ratio of the frame changes, it doesn't affect the resolution of the scene.

I play around with the 'Perspective/Focal Length' and 'Field of View' slides here to test out how I want the final image to look (the blue box in the image). After I have decided on the camera setting, I will click the little lock icon on the camera list in order to lock the camera, so I don't accidentally change anything later (pictured here in purple).

Cropping the image to our favored composition

Step 05: Assign materials

I then assign the materials by dragging and dropping the material balls from the library window to the parts where I want the materials to be. The parts that have the same color on the model will all be assigned with the same material.

After assigning materials, I can edit them by going to the Materials tab. The Diffuse color means the local color of the material, and the Specular color means the color of the highlight on the material. I set the Specular color to bright blue to suggest the color of the sky.

Assigning materials as we'd planned earlier

Step 06: Label system

Under the Materials tab, there is a sub-tab called 'Labels'. As well as adding labels, I also use it to add stains. I find a free stain texture online and turn down the opacity. Then I add labels and stains by clicking on the plus icon next to the label list. Anywhere on the material, the 'label' will instantly go to where I click. It's really convenient when it comes to stains and weathering effects that are not easily visible. I can duplicate labels by selecting the label on the list, hitting the plus icon again and choosing Duplicate Label.

Adding weathering and labels to the mech

Step 07: Environment lighting

After I have finished assigning all the materials, I move on to setting up environment lighting which will suit the park scenery better. Instead of using the default HDRI images in the library, I choose to find an image myself because I want one with a blue sky and green trees to reflect the colors of a park onto the model. I go to the Environment tab on the left panel and then click on the icon to the right of the 'Add new folder' icon to import my HDRI image.

After importing the image, I turn to the Environment tab in the project window and start to play around with the sliders to get the result I want. Hold Ctrl and drag with the left mouse button to rotate the HDRI.

Since I already have a modeled background, for the Background option, I choose to use 'Color', and I pick a color that's similar to the sky (pictured in the blue box). The flat color will help me later to quickly mask things out in Photoshop. For the same reason, I check off 'Ground Shadows' under the Environment tab in the project window (purple box), so I can easily mask out the mech's silhouette later in Photoshop.

Creating environment lighting using an HDRI

Step 08: Final rendered images

It is time to render out the images. Since I plan to create scratches and do much post-editing in Photoshop, I render out a couple of images with the exact same camera angle, but with different materials which will be the underlying materials of the cover paint.

I hide any unwanted parts by selecting them and then right-clicking and choosing the Hide Selection option. This speeds up the image rendering time considerably.

Fig.8a - Rendering out the scene ready for post-editing

Fig.8b - Different renders will give more freedom in the compositing process

Step 09: Texture compositing

When the images are ready, I bring them all into Photoshop. I put masks on all the images that I need, to simply for creating the scratches (see fig.09a, in red). The way I create scratches is by erasing the black mask from the images with textured brushes.

I also start to put in photo textures. The way I select the tricky, irregular shape of trees is with a masking technique. I first click on the 'Edit in Quick Mask Mode' icon in the tool panel (fig.09c, in red), and then I use a white brush to paint in the part that I want to select. After I finish painting, I click on the icon again to change back to normal mode, and the painted part will automatically become the selection.

Fig.9a - These masked layers will be used for weathering effects

Fig.9b - Erasing the masks with a textured brush

Fig.9c - Masking the irregular tree shapes

Step 10: Dramatic lighting

Lighting is one of the most important elements in a composition. I imagine a few lighting situations, such as dusk, sunny afternoon, twilight, a cloudy day, and eventually settle on a dawn-ish lighting. I think this is when the temperatures of the light and shadow are the most complementary, when the shapes of the shadows are most dramatic, and when there is still some heavy mist in the air.

I add a layer with the blending mode set to Color Dodge, then pick a dark-brown color to fill in the layer. I then add a mask to the layer and start to erase the parts where I want the light to show. I set the light coming from left, to lead the viewer's eye to the mech.

I then darken the mech and add in ambient occlusion by adding a layer with the blending mode set to Multiply, and then using the same masking technique as mentioned above.

Fig.10a - Choosing an early morning ambient light for the scene

Fig.10b - Adding ambient occlusion style shadows to the scene

Step 11: Further compositing

In this step, I start to edit the textures and add details to make them believable. I add a curb along the path. The connection between two objects, be they two mechanical components, a wall and a pipe, or in this case the path and the turf, is the key to believability. Furthermore, I look up some more references and decide to change the path to a more stone-like material. The technique I use here to make the texture match the perspective and shape I want is first by using 'Distort' on the texture, and then 'Warp'. I later erase the parts which I don't want (fig.11b).

In addition to adding more tree textures, I tune down the value contrast and color saturation in the far background. I also pay attention to the diminishing size of the far background trees. Both adjustments are for enhancing depth in the piece.

Fig.11a - Refining the environment and background

Fig.11b - Using the Distort and Warp transformation tools

Step 12: Final touches

I further adjust the value contrast to push the far background even further back, and then I look up more references and find that we usually can only see bushes for the far background, instead of the edge of the park, if we are deep in a huge park. Therefore, I add in bushes to enhance the believability of the scene. Observation of reality is the key of a convincing design, even for a fictional background story.

I also further darken the shadow on the path, and adjust the overall shadow temperature to be much more blue. I paint in some sunlight flare on the edge of the objects that are close and against the direct sunlight. Again, observation of reality helps me to add in tiny but super important details to enhance the believability. Some final cherries which I add are the light glare on the mech, and then some dead leaves on the ground.

Finally, I wrap up the piece by creating a Lens Blur effect to increase depth and make the viewers see the focal point first. In order to do that, I copy and paste the entire image onto a new layer, and then use the Gaussian Blur filter. I then put a mask onto the blurred image, and erase the parts which I don't want to be blurred.

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