The CARLA team prepares every asset to run under certain default settings. However, users that work in a build from source can modify these to best suit their needs.
This tutorial only applies to users that work with a build from source, and have access to the Unreal Editor.
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## Car materials
In CARLA, there is a set of master materials that are used as templates for the different parts of the vehicle. An instance of these is created for each vehicle model, and then changed to the desired result. The master materials can be found in `Content/Carla/Static/GenericMaterials/Vehicles`, and these are the following.
*__M_CarVehicleLigthsSirens_Master__ — Material applied to the sirens, if applicable.
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## Customize car materials
Create instances of the master materials and store them in the corresponding folder for the new model. Here is an example of the instances created for the police car available in the blueprint library, *vehicle.dodge_charger.police*.
<divstyle="text-align: right"><i>Instanced materials for the police car blueprint.</i></div>
Generic documentation for materials and how to work with them can be found in the [UE Docs](https://docs.unrealengine.com/en-US/Engine/Rendering/Materials/index.html). All the materials can be modified to a great extent, but only the exterior one has properties worth mentioning. Others have certain properties that can be changed, such as opacity and color in glass materials, but it is not recommended to do so, except for specific purposes.
### Exterior properties
The exterior material is applied to the body of the car, and it is the one that can be customized the most.
*__Base color__ — Base color of the bodywork.
*__Tint shade__ — Tint color which visibility varies depending on the angle of visualization.
*__Dust__ — A texture of dirt applied to the car. Dust is meant to pile on top of the geometry, and it is barely noticeable in the bottom parts. If the geometry is rotated, the dust will appear on the parts of the vehicle that are on top.
<divstyle="text-align: right"><i>Noise property in a car's material.</i></div>
*__Surface__ — Gloss and transparent coating applied to the vehicle's paint. This last step in [automotive paint](https://en.wikipedia.org/wiki/Automotive_paint).
*`ClearCoat` — Opacity of the coating.
*`ClearCoat_Brightness` — Glossiness of the resulting material.
*`ClearCoat_Metallic` — Reflection of the resulting material.
<divstyle="text-align: right"><i>Visualization of the Surface coating applied to a material.</i></div>
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## Building materials
The materials applied to buildings are made of four basic textures that are combined to determine the basic properties of the material.
*__Diffuse__ — Contains the basic painting of the material.
*`RGB` — Channels with the base colors.
*`Alpha` — This channel defines a mask that allows to modify the color of the portions in white. This is useful to create some variations from the same material.
*__ORME__ — Maps different properties of the material using specific channels.
*`Ambient occlusion` — Contained in the `R` channel.
Similarly to car materials, a building material can be greatly changed if desired, but it is only recommended if the user has some expertise with Unreal Engine. However, there is some customization available for the two main shaders that buildings use.
__RoadPainter__ is a tool that uses OpenDRIVE information to paint roads. To be able to do so, a blueprint is used, which uses a master material, a render target of the road as canvas, and additional decals and meshes. The master material grous a collection of materials that will be used by the blueprint, using brushes to blend their application.
This makes for an easy way to change drastically the appearence of the road. The initial geometry of the road is painted like a canvas. There is no need to apply photometry techniques nor consider the UVs of the geometry. The result is achieved simply by blending textures and creating masks.
<divstyle="text-align: right"><i>Panel to set materials to be applied on the road.</i></div>
__2. Set the `RenderTarget`.__ [Create a render target](https://docs.unrealengine.com/en-US/Engine/Rendering/RenderTargets/BlueprintRenderTargets/HowTo/CreatingTextures/index.html) for the road map that is being used. In `Texture Parameter Values` enable `Texture mask` and add the texture.
__3. Set the map size.__ In `Scalar Parameter Values` the field `Map units (CM)`. If the size is not known, use a temporary value. The real size of the map can be retrieved later, when using the blueprint.
__4. Choose the materials to be applied.__ There is space for one base material and three additional materils that will be used to paint over the base one. The painting information will be stored in the RGB channels of a RenderTarget, one channel per material. Add them to the fields `Base Material`, `Material 1`, `Material 2`, and `Material 3`.
The appearence of the road is changed using a blueprint provided by CARLA. The blueprint will paint the road using the materials passed, combined with some brush settings. Additionally, decals and meshes can be added so that the final result is more detailed. This tool takes into account road information and will paint the elements using the orientation of the lane, unless an offset is stated.
!!! Note
This tool does not interfere with the weather settings that change the road's appearence, such as wetness or precipitation.
__1. Create an instance of the RoadPainter blueprint.__ It can be found in `Carla/Blueprints/LevelDesign`. This blueprint determines how is the road being painted, and how are the materials in `RoadMaster` being used.
The `Z-size` option in the `Default` panel will give you the exact size of the map. Increase this by a little and make sure both, the blueprint and the master material have the same value.
__4. For each material, set the brush to be used.__ There are different brushes available in `GenericMaterials/RoadStencil/Alphas`. The materials will be applied over the road using the brush and parameters stated here.
*`Stencil size` — Size of the brush.
*`Brush strength` — Roughness of the outline.
*`Spacebeween Brushes` — Distance between strokes.
*`Max Jitter` — Size variation of the brush between strokes.
__5. For each material, apply it to the desired portions of the road.__ In the `Default` section, there is a series of buttons to choose how materials are applied.
*`Paint all roads` — Applies the brush to all the road.
*`Paint by actor` — Paints a specific actor being selected.
*`Paint over circle` — Paints using a circular pattern, useful to provide variation.
*`Paint over square` — Paints using a square pattern, useful to provide variation.
__7. Play around.__ Try different settings, materials and brushes to obtain completely different results. This tool allows to create different presets for the road appearence and changing between them simply by changing the group material and updating a few settings.
After the road's appearance has been customized, the lane markings should be updated accordingly to get a realistic look. The process to do so, is really simple.
__1. Create a copy of the group material.__ This has be the same as it was for the road.
__3. Mark them as lane markings.__ In `Static Switch Parameter Values` enable `LaneMark`. This will update the lane markings to be consistent to the painting applied to the road.
__4. Choose the color of the lane marking.__ In `Texture` set the `LaneColor` to the value desired. This will set the lane markings selected to have a base paint of the stated color.
