1. UVReactor Installation

Installing UVReactor is very simple! Just download the .zip file from the website:

Unzip it into a folder

Run the installer that matches your 3dsmax installation. The installer will guide you through the installation process. In most cases just hit the “next” button then finally the install button.

You’re Done with the Installation!

2. UVReactor UI

The UI of UV Reactor seamlessly integrate into the Max Qt UI. This means that all the UI elements are working exactly the same as the native 3dsmax UI.

The UI contains several elements, which are the following in the current BETA version. (Of course this will change in the future based on the added features.

  • Subobject Selection
  • Seams Display (Display)
  • UV Packing
  • Texel Density
  • Grouping
  • UV Topology
  • Flattening
  • Align
  • Rotate
  • Scale
  • Sort By Size
  • Backdrop Image
  • Modeling
  • About

The viewport is OpenGL accelerated, so you don’t have to worry about its performance.

In the forthcoming articles this documentation will guide you through each Rollups and their functionalities as well as how to control the viewport itself.

3. Viewport Handling

Pan and Zoom

The Viewport Handling mimics the Maya viewport pandling, which means:

  • Middle Mouse Button -> Panning
  • Right Mouse Button -> Zooming
  • Left Mouse Button -> Selection
  • Mouse Wheel -> Zooming

Selection Marque

To modify the selection, you have three modes to do that:

  • Left Mouse Button -> Normal Selection
  • LMB + CTRL -> Add Selection
  • LMB + ALT -> Remove Selection

Selection Add and Remove

Left Mouse Button Double Clicking:

  • LMB Double Click -> Loop / Element Selection
  • LMB Double Click + CTRL -> Add Edge Loop / Add Element Selection
  • LMB Double Click + ALT -> Remove Edge Loop / Remove Element Selection

4. Rollups

There are several rollups in UVReactor. Each one organizes actions that are responsible for a particular task. By clicking on the image, will lead you to the description page of that particular rollup.

4.1 Subobject Seleciton Rollup

The Subobject Seleciton rollup contains all the selection related tasks. All of them are UV SHELL BASED, which means that the system handles a UV SHELL as an INDIVIDUAL OBJECT.

For example if you perform a Loop or Ring selection, the loop won’t go through the seam.

To perform a certain selection on an object, you have to select at least one edge on a shell to count it into the modification of the selection.

Loop and Ring

Select By Smoothing Groups

Select By Material IDs

Select By Seams

Select Edges By Angle

4.2 Texel Density Rollup

Texel Density is a very important thing, especially in game development. This is the value that tells us the relation between the UV, the 3D Mesh and the Texture size. The unit of measure can be px/mm, px/cs or px/m etc… In our case it’s px/cm. (which might change is the future and possibly it will be attached to the System Unit)

Usually in game development, commonly used values are 5 px/cm, which means a 1024×1024 pixels texture will cover a 200x200cm area. This gives us an approximate 5.12 px/cm texel density, which is 0.512 px/mm or 512px/m. (in other a single pixel will be 2 mm)

The texture density is calculated using the following equation:

TD = √uvArea / √geoArea * tRes

Which is in short the square root of the uvArea divided by the square root of the geometry surface area, multiplied by the texture resolution.

You can get the actual texel density from a selection, which is always extended to an entire UV Shell, even if you have only a single face selected. The set also scales the entire UV shell even if only a single face/edge/vert has been selected.

4.3 Display Rollup

Ths Display Rollup contains two things only, but they are pretty important.

  1. The Seams Display Toggle
  2. The Mapping Channel

Display Seams

Mapping Channel

4.4 UV Packing Rollup

UV Packing in UVReactor is polycount independent, which means it will barely affects the speed of the packing. In other words the system doesn’t really take care of how many polygons you want to pack, it will not affect the performance. This is due to a technology that uses a model that can represent each UV shell in an abstract way.

The packing algorithm consists of 4 properties.

  1. Packer Resolution (this is not the resolution of the texture map, but the packing resolution) The higher the number leads the more precise the packing.
  2. Num Threads defines the number of threads for Multi-Threading. This value is the number of cores you want to use, minus 2. So on an 8 threads machine, it’s 6.
  3. The padding relates to the Packer resolution. In this case it will be 1 pixel for a 512 resolution. If you are using 1024 as the Packer Resolution, then it must be modified to 2, to get similar results.
  4. If the “Pack Selected” checkbox is checked it will pack only the selected UV shells, when you are working with a single object. In case of multiple objects the algorithm will pack everything.

Currently the packer doesn’t use any kind of heurestic, which means you have to find the ideal Texel Density for UV Shells. The packing is vert fast despite of that. The heurestics will be added later to the system and in that case the UVReactor will find the appropriate texel density for you, to get the best result.

Also the packing only supports the 0..1 space right now.

Note: If you have unselected shells in a UV Space, then the algorithm will keep them in their location and it will pack the rest of the UV Shells around them.

4.5 Sort By Size Rollup

This contains two simple algorithms that you can use to organize UV shells in a single row, by their area or by their fill size value.

The fill size value sorts all uv shells is a songle row or column by their boundary size and (uv area / boundary area) ratio. This way you can get an idea how the UV packer sorts the uv shells and in what order it place the uv shells into the uv space.

Currently the simple area based sorting is missing from the BETA build yet, but will be the part of UVReactor later.

4.6 Scale Rollup

The scale rollout contains all the discrete scaling options. With this panel you can scale each individual UV Shells around their center point. You can use negative values as well and it’s also possible to scale only on the horizontal or vertical axis.

4.7 Rotate Rollup

Rotate is similar to the Scale Rollup. It performs a discreet rotation on all the selected UV shells about their center points. This field can also handle negative values if necessary.

4.8 Grouping Rollup

Grouping currently is placeholder and it’s only suitable to store Selection Sets. If you are using UVReactor (means that UV Reactor is open, it updates the underlying data structure after each modification, so all of the faces inside a UV Shell will use the same ID, even if you are modifying the toplogy of the geometry or the UV.

Note: the update choses the most frequent ID in a UV Shell and it will change all the rest of the IDs to that one.

4.9 Align Rollup

Edge Align is a simple tool to rotate your UV shells horizontally or vertically based on an edge selection. It is especially useful, when you want to align UV shells to the horizontal or vertical axis of the UV space.

The selection can be average in the same shell and it can be used on multiple UV shells as well.

4.10 Backdrop Image Rollup

The backdrop image rollup is a simple solution to load in any kind of texture into the background, so if you have tiled textures, you can properly align the uv shells. You can also modify the opacity of the backdrop image if necessary.

Later I’ll update this functionality, like using the image from the actually used textures from your scene or with UDIM support or even with automatic Material ID assignment.

Note: the loader uses the build-in max image library so it can hangle the same image formats as 3dsmax.

4.11 Modeling Rollup

This one is a bit odd-one-out, because it’s not necessarily UV editing, but using UV data to do certain tasks.

The Smooth By UV Shells makes it possible to turn smooth edges to hard edges or hard edges to smooth edges based on the angle along the UV seam. This was a request.

In the future, I’ll extend this panel with other functionalities.

4.12 Flattening Rollup

The flattening rollup is one of the most important part of UVReactor. Here is the place where you can relax your UVs into a non-distorted UV shell. The algorithm is very fast and prevents triangle flips in most cases. (currently overlaps can still occur)

Flattening with UV Reactor

The flattening needs an initialization, which you can do with the Init Circle Button and then clicking on the Flatten button will relax it into a non-distorted state. The Initial state can also use a square boundary.

UV Reactor Planar

The planar mapping in this case differs from the one you can find in the Unwrap UVW modifier. This planar mapping always uses a plane perpendicular to the average normal of the geometry faces that constructs a UV shell.


The straighten algorithm in UVReactor easily outperforms the one that can be found in the native UnwrapUVW modifier. This algorithm averages the loops to get create a flattened UV shell.

There are still distortions if the rope have different diameters, but this will be fixed in the future.

4.13 UV Topology Rollup

UV Topology is the other crucial part of the system. It consists of two functions.

  1. Stitch
  2. Break

Stitching Seams

Stitching can use Snap To Selection which is turned on by default. This feature also resizes the UV shells to match the size of the target. (it caluclates the scale using only the edge selection and not from the texel density)

Breaking Seams

Note that breaking seams can be done using EDGE and FACE selection as well.

5. Reporting Bugs

If you have found a bug or crash, please join to the RapidMXS Discord Channel. There you can create new posts in the bug-reports section. https://discord.gg/pevXtxe3S2

Before reporting a bug, please try to search before posting. This way I can keep the entire bug tracking much cleaner. If you are an experiencing issue not already reported, please let me know and if possible, provide me example files and/or videos, so I can reconstruct the bug for testing purposes.

6. Troubleshootings

Slow UVReactor Startup

In certain cases launching UVReactor is very slow. In this case try changing your OpenGL video card your native video card inside the nVidia Control Panel.

Device Init

Corsair Keyboard

This solution (may work or not) comes from a topic from GitHub, where someone else had a similar issue.

good news..no awesome news….i just update drivers corsair k55 driver from the web site and installed the software for it …the problem did not go away but then the keyboard software did another update itself..and the problem is gone…i tested hitting F5 30-4 times in a row while 7 you tube videos and unreal engine open and 3 other visual studio project open…i also had another project with the opengl and tried even that one at the same time…no problem the window opens 565-650 milliseconds and never slowed down…Before it was taking 20-40 seconds when it slowed down…..so the issue is closed thank you guys for the support i could never think it would be keyboard and thinking it is GPU causing conflict with GLFW Anyway….thank you all of you..i will be happy to help if i can anyway …thnk ..it is a good day for me :=)

GitHub Link -> https://github.com/glfw/glfw/issues/1709