Week 3: Bark and Tree Trunk

    This week I started on the bark and tree trunk. For the bark, I used Substance Designer to mix some small chunks and gradually build up a layered bark effect. I think it's kind of getting there, but I feel like the crevices between the bark chunks may need more definition.

    To create the initial layers, I made 4 different bark chunk shapes and arranged them on 3 different tile samplers which I combined together. After making that initial height map, I varied up the shapes with warp and slope blur nodes.

    After making the bark, I applied it to my tree trunk in SpeedTree. The branch shapes will most likely need more edits, but I will probably get more ideas on what to change once I add the canopy.

    Other than that, I also made Spanish moss and added it to some of the branches. I had a lot of trouble placing them, so I'm still looking for a good way to hang them quickly and believably. To generate the textures, I learned how to use FiberMesh in ZBrush. Once I had the high poly, I simply baked them onto a low poly plane and used the maps to generate a base color in Substance Designer. Eventually I want to pack a few more variations into the atlas. For now though, I just kept it to 4 pieces so I could test them out in SpeedTree.

FiberMesh Process

Final High Poly

Final Textures

That's all for now! Next I'm going to start on the canopy and rework the trunk, bark, and Spanish moss as necessary.

Week 2: First Plant

 This week I created materials and meshes for my first plant type. 

 

One new technique that I used is generating the materials in Substance Painter. Since I had height information from the ZBrush sculpt, I could create a lot of variation with fill layers and generators. As an example, I used the "Dust Dirty" smart mask to make the leaf veins yellow.

Since the ZBrush leaves had different Polygroups, I also baked an ID mask. With this mask, I created a different color overlay layer for each leaf. This made it so some leaves could be a little more yellow and others more blue-green. This subtle variation adds some more contrast to the plant so the leaves don't feel like they're all one flat color.

Example of some of the different layers used.

Overall I think it's off to a decent start. Next I'm going to start on a tree. It should be a great way to better familiarize myself with SpeedTree!

Southeastern Forest Scene Week 1

 Over the next couple of months, I'm taking a foliage class. I'll post my weekly progress here. This scene will be a southeastern conifer forest based on some nearby parks that I've visited.

For this first week, I gathered reference, created some sketches, and started on the leaf atlas. It's been a while since I last used ZBrush, so this has been a great refresher. 

Other than that, it's also my first time using PureRef to organize reference photos. So far I really like using it. Previously, I usually put reference photos together in Photoshop, but this is more flexible and easier to use. Compared to Photoshop, the main thing that I like is how you can keep adding full resolution images and increase the canvas area without performance getting affected.

For my sketch, I also experimented with a new technique where I make separate layers for local color and lighting. I enjoyed working this way because it somewhat mimics 3D rendering. I definitely want to try it again on future sketches.

Additionally, I practiced perspective with this. The main thing I focused on was approximating the cone of vision to make sure nothing gets distorted in the shot. I found this helpful page explaining cone of vision: https://courses.byui.edu/art110_new/art110/week02/cone_of_vision.html. 

Following the video, I made a circle bigger than the image and then made sure it was about 60% as wide as the distance between the vanishing points. This should give a standard 60 degree viewing angle.

To create the leaf atlas, I sculpted one leaf and then duplicated it a few times. With the deformation, move, and clipping tools, I bent the overall shapes and added some damage to vary them up. The cylinder on the left is a placeholder for a tiling stem texture.

That's it for the first week! The next step is baking this atlas and creating materials in Substance Painter.

How to Convert World Space Normals to Tangent Space

    Recently, I ran into some shading issues using a world space normal map on my billboards. When instanced meshes have different rotations, it seems Unreal Engine can't keep the normals consistent. Since Unreal's imposter baker creates world space normal maps, I needed to find a way to convert them to tangent space.

 

Billboards with world space normals.

Billboards with tangent space normals.

    To fix this issue, I converted my world space normal map to tangent space with xNormal. Here are the steps that I took.

1. First, there are two things that you need. One is the source mesh, and the other is the world space normal map baked from that mesh.
   
   
   
   
   
   
2. Rotate the mesh to match xNormal's coordinates. I don't yet know a great way to figure this out, so I just guessed until I got it working. For me using 3ds Max, I rotated the mesh 90° in X and 180° in Z. Make sure to reset XForm before rotating. If there are already transforms on the mesh, this will interfere with how xNormal interprets the orientation.
   
   
   
   
   
   
3. Export the mesh as an obj file. These are the settings that worked for me.
   
   
   
   
   
4. Go to the tools section in xNormal, open the object/tangent space converter, enter the settings for your mesh, and generate. In this case, Xnormal is actually converting from object space to tangent space. So long as you didn't move your mesh from it's original pivot point, it should work fine with world space normals.
   
   
   
   
   
   
5. Check the output tangent space map. It should look something like this. This is close, but you will still need to edit some of the channels so it's compatible with Unreal.
   
   
   
   
   
6. Look at the individual RGB channels of the map in an image editor, such as Photoshop. If you imagine a light shining from the edges of the image, you can get a sense of how the channels should look. In this map, red is coming from the left, green from the bottom, and blue from the back. For Unreal Engine, you want the red from the right, green from the bottom, and blue from the front.
   
   

   

   These are the original axis directions in the baked tangent space map.

   
   

   

   These are the directions needed for Unreal Engine. In this case, the red and blue channel are inverted.

   
   
   
7. Invert the red and blue channels of the texture. I used Substance Designer for this. Using an RGBA split, I inverted the red and blue channels and then re-merged them. After that, I used the alpha channel to make a mask for the background areas. To expand the edges of it a bit, I used edge detect. After that, I filled the area with the default normal map color. This should prevent any artifacts on lower MIP maps in the texture.
   
   
   
   
   
   

   

   The final normal map.
   

   
   
   
8. Finally, import the normal map into Unreal. There are two options for how you can import it. One is importing it like a standard normal map without changing any settings. For the other, you can import it as a linear color texture and then adjust it in the material. I opted for the linear color because it seems to take slightly less space.
   
   
   
   
   
   
9. If you want to use a linear color map, change all settings to default and uncheck sRGB. Whenever you use it in a material, make sure to add a constant bias scale node. Set the bias to -.5 and scale to 2.
   
   

   

   Linear color texture settings.
   

   
   
   

   

   Make sure to add a constant bias scale node anytime you use a linear color normal map.
   

   
   

    That's it! You should now have a functional tangent space normal map.

 

Lighting and Skydome Progress

     Lately, I've worked more on the tea mesh, the lighting, and the sky dome. My goal is to make it feel like a cloudy early morning. I think it's getting a bit closer, but I still want to layer in more clouds in the sky dome. In addition, I'm planning to add some flow maps and panning noise textures for animation.

    Next, I'm going to work on the cloud cards that are placed in the level. I think they're too translucent right now, and I want to give them more of a sense of volume. Another thing that I want to do is make the ground less flat looking. If I make a ground cover mesh and perhaps add tessellation and more roughness variations to the terrain materials, that should help give it more depth. Overall, I think those will be some good goals to work on next. Afterwards, I can continue refining the tea mesh and sky dome.

Progress on Landscape Materials

        Over the last couple of weeks, I worked on landscape materials. I thought this project would be a great opportunity to get more practice with Substance Designer. Following the "Forest Ground" tutorial by Get Learnt w/ Chunk, I made a ground generator to create three main material variants.

        I also followed a tutorial by Bohdan Bilous to create a terrain generator. Right now, I'm only using the color as a macro texture for the landscape material. I'm planning to use it for the background mountains later on too. Basically, I just blended between the close texture and the macro texture based on the distance between the material world position and the camera.

        Next, I will add more variations to the ground materials and work on a custom cloud mask for the sky. Additionally, I'm going to revisit the tea plants too. I think they could use a bit more dimension and negative space to them, so I'm going to see if I can add more cards and rely less heavily on the filler mesh that I'm using in the center of the plant.