In this month’s Tips & Tricks, Darren Chilton discusses using RenderQ to process batch renderings, including batch rendering setup for images and animations. Click on the video below to see these tips & tricks in action.
Rendering TipsCategory Archives
Tips & Tricks: Rendering Basics
In this month’s Tips & Tricks, Darren Chilton discusses the options available in solidThinking to help you work more efficiently and create better quality images. Click on the image below to watch the video for tips on:
- Using global illumination for more realistic lighting
- Using ground planes for shadows and reflections
- Understanding options in the Shading Manager
- Navigating in the Material Library
- Using Oversampling Parameter to increase image quality
Tip: Controlling Shadow Production for Each Object
The production of shadows in solidThinking can be controlled for each object in the scene, as well as for each light.
All objects will cast and receive shadows when illuminated by lights which have the shadows enabled (note that by default shadows are disabled).
However, there may be situations where this is undesirable, for instance, certain objects cannot produce a visible shadow, due to the viewing position: excluding these objects from shadow calculations can result in improved rendering performance; both in terms of increased speed and reduced memory usage.
This can be performed very easily through the World browser (in case the panel is not displayed, you can open it by choosing Managers > Browser). By right clicking one or more selected objects in the browser, a popup menu appears allowing you to instruct the program as whether an object must Cast shadows or not and whether it must Receive shadows or not.
You can resort to these options also to illuminate certain areas of a scene without creating shadows, without the need for a complex system of ‘fill’ lights as would be used in a theatre or movie set.
Tip: Lighting an interior with just one light
Lighting an interior that only receives natural light through doors or windows can be a difficult task. In fact, for the most part, the lighting of the interior comes from the light bouncing off the walls, floor and ceiling. In order to achieve a good result, this ‘bouncing’ must be handled properly. Here is a tip on how to obtain good lighting with just one light source in a scene like the one represented in the image below.
This scene does not contain any light. In order to simulate the natural light, follow the below steps:
- add a light to the scene using the Light tool that you find in the modelling toolbar;
- place the light anywhere in the scene;
- open the Shading panel, right-click on “Light [none]” in the shader tree and choose “simple sky”.
Now we need to adjust intensity and shadows. Set them as in the picture below.
At this point, if we render we can have an idea of where the direct lighting hits the floor (see image below). The scene is dark because we have not yet activated the ‘bouncing’ of the light.
In solidThinking, there are different ways to activate and control the light’s bouncing. In this case we will use a method that provides extremely fast, high-quality and natural-looking results.
We use the Final Gather algorithms that we can activate in the Rendering section of the Shading panel. Once it is enabled, we just need to control and adjust some parameters, as shown in the images below.
Once we have set these parameters, we can render and see the final result (see image below).
Tip: Using the Shadowcatcher shader
The Shadowcatcher is a unique shading property that allows the object(s) with this particular material to be invisible in the rendering but stll accept and display any shadows cast upon them. This is typically used to integrate a 3D object into a photographic background where the object would not normally have a shadow.
To use it, you can add on or more ground planes to your scene where you want the shadow to be cast.
After selecting the ground plane(s), open the Shading panel and choose the Surface Material tab. Right click the Reflectance shader component to assign the Shadowcatcher type. Various parameters are available. When the scene is rendered, shadows will be realistically cast upon the ground plane(s).
Tip: batch rendering with rQ
solidThinking comes with a standalone batch-rendering application called “rQ.” This can be used to render a number of images or animations automatically, in a predefined sequence. This is especially useful if you have very large images or scenes to render or if you are creating a number of “variation” images of a certain design. There is no need to wait until the rendering finishes and start the next one manually – simply load them all into rQ, press “Start” and come back hours (or days) later and find all of the rendered files safely on your hard drive!
What follows is a visual summary of setting up and batch rendering your files using rQ. There is more explanation in the “Help” files for the application (accessible through the Help button at the bottom of the main screen), and the options available for features like animations and image rendering outputs are too numerous to cover completely here.
The rQ application is installed, by default, in the same folder as the main solidThinking application. When you launch rQ, it also launches a “background process” of the main solidThinking applicationto read all of the file variables for each rendering. The objects, lights, cameras, materials and render settings are all saved with the solidThinking file (”.st”), and the rQ utility reads these settings and runs the renderer to produce the images and animations that were last set up and saved in each .st file. Therefore, it is important to save your files for batch rendering with all of the desired render settings (method, resolution, frames, etc.), visible objects, and correct materials before launching rQ.
The main rQ window (seen in the image to the right) has three working areas: the Queue, where you add and arrange files; the Output location for each file; and the Render controls and progress indicators. The Output Directory can be defined for each file by selecting it from the Queue and browsing to a directory; and the Render controls are for all files in the Queue, starting with the top most file.
When you add files to the Queue, the individual File Properties dialog will come up with options for the render. This dialog allows you to choose whether you want to render a static image or a full animation (if one was saved with the file). You can also choose which camera view to render from as well as the animation frames and “video codec.”
Because animations in solidThinking are saved as single video files, you must choose a codec (compression-decompression scheme) for the output file. Similar to saving a single image for the Web, the video codec and its settings will determine the visual quality of your final animation video. Press the “Video Codec” button to bring up the selection dialog (seen to the right). The types of codecs you will have available depends on the global codecs installed on your computer, but they will include the basic QuickTime options that were installed with solidThinking.
The still images produced by rQ will be in the file format defined in each file. You can find the image format settings in the Shading panel, under the “Output” tab, and set this for each file to your preference.
Tip: Adding Lights to the Scene
When you render different solidThinking scenes without adding lights they have the exact same lighting. This is because solidThinking places a ‘default’ light source in the scene if there are no other lights present. Without a light source all of the renderings would be completely black, since all objects are only visible when there is some light hitting them to allow our ‘eyes’ to see them.
When you add a new light to your scene, solidThinking will automatically disable the default lighting, allowing you to design the scene as you would like. This is why it sometimes seems that the scene goes ‘black’ if you simply insert a lightinto your scene. You need to point your light source at your objects.
Tip: Environment Lighting
The quality of a rendering picture often depends on the lighting of the scene. Images can be used as environments (via the “environment” light shader) which illuminate a scene (allowing digitally created objects to be rendered with lighting conditions exactly matching some real world scene).
Although HDRI Images (.hdr) are not required for the environment lighting technique, they can can represent a much higher range of intensity values than traditional image formats, which only represent the range of intensity values which can be displayed on a computer display.
The picture shows how lighting changes with different images used as environments.
Tip: Final Gather
This tip will focus on a single new technology that has been added to the renderThinking renderer, called “Final Gather.” Although the title of the feature is a bit esoteric, the net result is a way to very quickly and efficiently simulate many of the effects of Radiosity light transport in standard renderings. Unlike the full Radiosity rendering option in renderThinking, Final Gather only does “one bounce” radiosity and sacrifices some precision for increased speed, but the effects can be incredibly realistic and in many cases just the trick for higher realism.
As the image animation to the right illustrates, adding Final Gather to the “rendering chain” (what is computed before and after rendering to make the image) of certain scenes can dramatically enhance the realism and illumination of surfaces and objects. To start with, you can see in the illustration that simply Raytracing the “Cornell Box” in the scene provides a fairly dark image, with black shadows and grey walls (that are actually white). This image took about 5 seconds to render on a fairly slow computer.
By going into the Rendering tab of the Shading panel in sT 7.5 or 7.6, and simply adding “Final Gather” to the render, the side walls “bleed” their bright colors onto the white surfaces and the illumination from the point light at the top of the box reaches even into the shadow regions because it “bounces” off of the walls – just as real light would. Adding this irradiance to the scene (with the default quality settings) meant that the image took about 6 seconds to render. A very small increase in rendering time for a very large increase in lighting realism!
The last image in the animation (Final Gather “ON” (more precise)) shows the possible refinement of the scene by doubling the Number of Rays cast by Final Gather in the scene, and by decreasing the size of the samples so that they can detect smaller changes in color in the scene. The results are the fairly subtle brightening of the walls where the white squares on the floor touch the walls and objects (while the black squares bounce no light), and the smoother gradations of shading on the walls and on the sphere in particular. Changing these settings meant that the render time went from 6 seconds (at the default settings) to 20 seconds for this very simple scene. (Each scene will be different, but in general, this is much faster than using the full Radiosity render option!)
In addition to being able to “tweak” the Final Gather settings to increase precision or calculate things like specular bounce (for very shiny surfaces), there are also very simple adjustments for the saturation of the irradiance (for example, so the blue and red walls do not overly “color” the scene as in my example), and also for the overall brightness of the Final Gather effect (to make the irradiance more dramatic or more subtle). These simple additional adjustments also do not change the time it takes to render the scene with Final Gather on!
