Rendering Graphics

This page describes how you can render graphics within blender for use in FreedroidRPG. It does not cover the basics of blender, and is a bit incomplete. Feel free to help improve it.

In this page, you will learn how to:

  1. Make item graphics
  2. Make obstacle (map elements) graphics
  3. Make animations for Tux and NPCs

The Git repository containing the graphics sources can be browsed through a web browser in []. Individual files can also be downloaded from there. Alternatively one can use a Git client and download the whole repository.

If you have questions that weren't answered by this article, feel free to send a mail to the mailing list or ask on the #freedroid IRC channel on Libera Chat. See our contact page.

The Render Scripts

The first thing a graphics army artist working on FreedroidRPG will encounter is the scripts. For rendering every type of graphic asset in the game except items, a python script is used. The scripts are run from inside Blender, and make much of the workflow of rendering and integrating the graphics into the game automatic. They are found in the render_scripts/ folder in the graphics repository (and, in the .blend source files, they are usually found at the right of the screen). They are all different, specialized for each type of asset (obstacle, Tux, NPC, or floor tile), but they all do one very important thing: they calculate the offset of the image displayed in-game, using simple mathematic operations on location data and properties of the camera. They then call the Croppy program, packed with the FreedroidRPG release, to crop the rendered image. Information on the function of individual scripts can be found in their respective asset's section.

The scripts use the API of Blender's python modules as of version 2.58a; using them with previous versions simply will not work.

For the scripts to work, firstly they must be loaded into Blender's built-in text editor. Next, the parameters inside the script must be set to their correct values; their names are usually self-explanatory, and specific instructions can be found at the top of each script. Afterwards, the "Register" checkbox at the bottom of the text editor window must be checked. This means the script is considered by Blender to be a module, and it is run automatically when the file is loaded. Now, the big "Run Script" button next to the checkbox must be clicked.

The script is now ready for action every time the file is loaded; all that is required to do is to start the animation by pressing the ANIM button found in the Render section of the Properties tab (a nice graphist will leave it in plain sight when saving the file!) or, by default, via Ctrl+F12.

Inconsistencies and code insanity is likely, considering the scripts were written and re-written by different people at different times with different requirements.

Rendering an item

Open up blender and load the model. There are three things to render : the inventory image (inv_image), the on-the-ground image (ingame), and the little rotational video (portrait) that is seen in shops. We will do things in this order.

Inventory image

As far as the inventory image is concerned, the only important thing is to pay attention to the size of your final image. The game by default uses 32x32 pixels per inventory square in game. However, creating small images only 32x32 or 32x64 in total size severely hampers flexibility later on when balancing the items size, without the image becoming ugly. Using a higher quality image, for instance 64x64 pixels per inventory square, is usually an advantage.

Place the camera the way you wish, go to the Render section of the Properties editor, and set the format to PNG, RGBA (A stands for alpha, meaning transparency, and we need it in FreedroidRPG) in the "Output" subsection. Set the appropriate image resolution in the "Dimensions" subsection. Press F12 to render the image; when it is done rendering, press F3, which will change the window under the cursor into a file browser; save your rendered PNG under the name "inv_image". If you are preparing graphics for an item that has been implemented already, all you have to do in order to test it ingame is to replace the images in the item's graphics folder in freedroid/graphics/items. If your item is in planning, you will need to copy and paste an entry for it in freedroid/map/item_archetypes, and set the path for the graphics.

Ground image

The ground image is seen when the item is laying on the ground, and the way the item appears is mostly up to you. The camera should be set to "Orthographic" mode in the camera panel, accessible from the Properties window, since the game world is isometric. It then must be moved and rotated around the item so that it appears lying down when rendered (press F12 to render, numpad0 to go to camera view, and shift-F while in camera view to enter fly mode; roll the mouse wheel up to fly forward, down to fly back, left-click to accept, right-click to cancel and return to the original position).

The one thing to remember is that the size of the image must be logical; you can use the size of ground images of items that are about as big as the one you're trying to render for comparison. Render the image in RGBA PNG format, and save it as described above under ingame.png. An offset file must be generated: Croppy is a program that does that, as well as cropping the image, and can be found in freedroid/croppy. Run croppy -i [imagename].png in a command prompt, and you will have an offset file. The numbers may require tweaking afterwards, so it's important to test the item ingame before submitting it.

Shop animation

The shop animation (or "portrait") is a little animation of the item rotating. In most items it is composed of 32 frames, although the number is flexible and the game will accept numbers below that and will display every image in the folder up to the 32nd one. This is generally inadvisable because less frames result in lower quality.

The size of the images is 132*180 pixels, and they must be saved as "portrait_" (simply put that in the output text field, blender takes care of the numbering itself). The file type is JPG, in RGB format; the background color needs to be black. This can be set in the World panel, found always in the Properties window, either by changing the Horizon color to black or by simply pressing the little X button next to the namefield, removing the World material.

If your model is composed of many parts, create an Empty (space > add > empty) and parent all the parts to it. You will need the camera to get a good view of the item, and take care that no part of the item is outside of the view, at any point during the animation. Use keypad 0 to change to camera view. To set the first keyframe, go to frame 1. Select the object or the empty, and press I. From the menu select "Rot". That sets a keyframe for the object/empty's rotation. Now, go to frame 33 (or the number of frames you wish to put in the animation + 1). Press R, then Z, and type in 360. This rotates the selected object by 360 degrees

  • a full turn - along the Z (vertical) axis. Make another rotation keyframe the same way you did the first one.

To make the rotation smoother when looped in the shop animation, we need to edit the animation curves. Split your window (move the cursor below the top header, it changes shape to a "resize" cursor - right click, select "split area"). On the left of the header of the new window you just created, select the Graph editor. With the rotating object selected, you will see its curve for the rotation: X-axis representing time in frames and Y-axis representing the value of the parameter. Select that curve with the left mouse button, and press T. From the "Interpolation mode" menu that appears, select "Linear". That will make the animation progress linearly over time, removing the smooth start and finish which makes the animation look funny when looped.

At the Scene context buttons (F10) set the animation to run from frame 1 to 32 (or, again, the number of frames in the animation). Rotating the object 360 degrees over one frame more than what is rendered is done so that the animation is looped well - the object almost completes a whole turn and returns to its original position, and then the first frame is displayed again, so no image is a duplicate of another. Hit the big "ANIM" button, and enjoy.

Rendering an obstacle

Rendering an obstacle is fairly similar to rendering the video for the item. However, the size of the image - and the surface actually covered by the obstacle - matter a lot, and camera position relative to the obstacle is of tremendous importance.

We assume you have your model done and ready for rendering.

Camera setup

It's simple and easy to import (using the File menu or the shortcut Shift+F1) or even link (Ctrl+Alt+O) the object name RotoCamera from any other obstacle source file. Alternatively, the setup can be created from scratch. The projection used on the rendering is isometric. What you will have to do is to set the camera mode to orthographic, and place it correctly on the field. To do this, select the camera by right clicking on it. Press the "N" key to bring up the transform properties window. Set its location on the X axis to 1.5, Y to -1.5, and Z to 4; all Scale parameters to 1.0, its rotation on the X axis to 60, Y to 0, and Z to

  1. Hit "F12" to check the positioning of the camera, and move the object if necessary.

Make sure that in the first frame (frame 1) the object is facing east according to the ingame compass (negative Y in blender) when rendered. For every frame it must rotate negative 90 degrees so that in the second frame it faces south, then west, and finally north.

Select the camera. In the Properties window click the button with the camera icon. There, click the "orthographic" button so it is enabled, and then choose the scale value so the result has the size you wish to give it. 7.35 is a good default value.

Scene setup

Now in the "Render" panel (always accessible from the Properties window) select PNG format, RGBA, size 200x240. Do the animation stuff for 4 frames so you get the four angles (see above). Hit the ANIM button.


The render script for obstacle rendering runs the images through the croppy tool, which surprisingly crops the images. However if, for any reason, the process of making the obstacle images did not involve the render script in blender, this can be done manually. cd into the directory where croppy is compiled; usually this is a subdirectory in the FreedroidRPG install directory. Then run croppy -i the_png_file.png for each of the files. It will automatically generate offset files that may need a bit of tweaking afterwards but should be mostly OK.

Integration into the game

Open up src/defs.h, look for NUMBER_OF_OBSTACLE_TYPES. Right above this line, add the symbolic names for your new object (four of them, one per cardinal direction).

Now open up map/obstacle_specs.lua. Copy an entry for an existing obstacle, and add it to the end of the file. The parameters, such as the image filename and borders, need to be adjusted.

Start the game. In the level editor, which is by default in obstacle mode on startup, select the "ALL" tab. Scroll to the end of the bar (using the pagedown button would help), and place the new obstacle to test its appearance and behavior ingame.

<basse> setup for wall and floor pieces animation is simple: all pieces are
parented to an empty object. that empty object is animated once, to advance
correct amount in one frame <basse> then that is repeated to infinity<br/>
<ahuillet> how do you animate it? how do you repeat it to infinity?<br/>
<basse> select empty. hit "i" insert location key. move empty, hit "i" again and
insert location then go to curves and set interpolation mode<br/>
<ahuillet> "linear" mode I guess<br/>
<basse> yes<br/>
<ahuillet> and that's enough for an infinite repetiton?<br/>
<basse> yes, well, if you look at the curve you see it just goes on and on..

Tux & NPCs

This part of the documentation is subject to change in the future. It is written for Blender version 2.5 and onwards.

The Basics

The first thing to know about the Tux images is the following: Tux is divided into parts - legs, arms, head and so on - and is put back together by the game. To be displayed in the game, the images are packed into a texture atlas, a single large image that contains all of the smaller images with a text file that contains "instructions" for the game to find each image.

Whether you want to update an existing animation part or make a new one, the make_atlas script is used. It is found in freedroid/gluem/, and takes several parameters. They are, in order:

  • The name of the atlas image that will be produced; it must end with an underscore (_).
  • The second and third parameters are the width and height of the atlas, respectively; they must be powers of two. A good default value is 1024x1024; if the part is small and a large part of the atlas is unused, they height can be reduced to 512, 256, etc.
  • The output filename for the text file, which must be simply atlas.txt.
  • The input image; *.png will pack all of the images in the working directory.

How to generate a new tux_image_archive

  1. The source file for the Tux motion is required - there are several types of animation (1-handed melee weapons, 2-handed ranged weapons, etc.) and they can all be found in the tux_motion_parts folder in the git repository.
  2. The objects we want to see on Tux must be imported into the .blend file (using shift+F1). They must be moved and rotated to fit on the armature so that they look well when shown with the rest of the parts, and be parented to their appropriate bone. Thus weapons must be fitted so they're the right size relative to tux, aren't hidden by the weapon arm, be parented to the weapon bone, and be on their own layer with no other parts on it. Jackets must be parented to the head and rendered with the torso, and so on. It's possible to consult the image atlas of another item of the same type to see how it needs to be rendered.

Make sure the rendered images are in PNG, RGBA format, and that the camera is orthographic and at scale 4.81, an option that can be set under the Camera buttons in the Properties window with the camera selected. Hit the Animation button in the Properties window (or Ctrl+F12). Now you can go make a cuppa. :)

After the rendering is finished, the cropped files can be found at the folder you indicated in the script earlier.

Congratulations, the animation is ready! Now you can send it over to the project managers for them to review and implement!

NPC Animations

Unlike Tux, NPCs and droids don't come in pieces; also, they have specific names for every phase of the animation - stand, walk, attack, gethit and death. The corpse of the NPC is the last frame in the "death" animation.

Before animating the NPC, remember the phases of its animation must be repeated 8 times as the camera rotates around the NPC. This is done through actions; each phase of the animation is a separate action, and they are repeated in the order above 8 times - simply by duplicating them in the NLA editor.

After rendering, the make_atlas program must be run, see the instructions above for rendering Tux parts. Voila! The animation is ready to be sent to the project managers!