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    INTRODUCTIONWalkthrough animation is a special kind ofanimation, where the only thing moving in the sceneis the camera.You can see an example of a walkthrough animationat the Thea Edition 1.2 Tutorials page (a preview ofthis animation is also seen in Figure 1).At this tutorial we will see the way we can preparesuch an animation for rendering, by giving the mainsteps to set up the animation and make the neededadjustments for faster and smoother results.Along with this document you are welcome todownload the corresponding scene to see thecamera and engine settings.

    Figure 1: Walkthrough Animation

    SET UP A WALKTHROUGH ANIMATIONThe first thing that one needs to do for creating a walkthrough animation is to make a cameramove around the scene and create its motion.Like all other animated objects, motion to a camera is applied by the following steps:1. Open the Animation Toolbar (see Figure 2) for setting up the key frames of the animation.2. Move the selected camera at the point the animation will start and set up a key frame at

    the corresponding frame (zero for example). For adding a key frame you need to use thewhite key button as seen in Figure 2.

    3. Go then to a different frame by dragging the frames bar. Move your camera to anotherpoint of the scene, adjust its view accordingly and set up a new key frame.

    4. Follow the previous steps as many times as needed for creating the animation of thecamera. You can see the path of the camera with a blue line and with green dots the keyframes that you have set up (see Figure 3).

    5. You can go to the selected camera view and play the animation to see the way the cameramoves around your scene and make any needed adjustments.

    Figure 2: Animation Toolbar

    Version used for this Tutorial: Presto Edition v1.2.05 Build 916

  • Figure 3: Camera Animation at our case study sceneBlue line shows camera motion and green dots represent the defined key frames

    Tip: in order to get a smooth and nice animation, try to use an appropriate speed for the cameramovement. Camera speed affects both the render settings that we will make (as explained later)but also how good our animation will look like. Very fast camera movement could be unrealistic.By using a frame rate of 25 for example, means that each second of our animation will be shownby 25 frames. Within this second, if we have made the camera move for example along a 10meters distance in 25 frames, our animation would be too speedy. Slower camera motion mayrequire more frames but the final result will be much smoother and natural.

    MAKE ADDITIONAL SETTINGSAfter creating the camera motion, we need to make someadditional adjustments at the Animation settings panel inthe way we do for any other animation. At the Frames panel, as we see it in Figure 4, we can specifythe total animation frames, the frame rate and which frameswill be rendered (all, current one or selected frames).Here one can write either frames numbers separated bycomma or by dash or a combination of these. For examplewe can type: 3, 4-8, 12. The frames that will be finallyrendered will be the 3, 4, 5, 6, 7, 8 and 12.We can also select the Frame per Bucket|Pixel option fornetwork cooperation. Figure 4: Animation Settings Panel

    The most important panel here (for our case) is the Walkthrough panel. At this panel, as its namereveals, the settings for the walkthrough animation exist. Note that these settings are used forthe Adaptive (BSD) engine only. If the scene is set up as described above (you have used a camerato move around your scene and no other movement exists) and you have used the Adaptive (BSD)engine, you can enable the walkthrough animation option of this panel for making render timesfaster and final animation smoother.

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  • PREPASS LEVELPrepass Level: from this drop-down list (see Figure 5) you canspecify the desired Prepass Level for the walkthroughanimation, meaning the irradiance computation per frame.More precisely, the prepass level in the animation panel will"average" or "smooth" the differences in Global Illumination(GI) calculation between frames.

    Figure 5: Prepass Level Values

    With the prepass level enabled, Thea will average the frames Global Illumination and with thisway if any artifacts exist in the scene, they will not flicker at the produced animation.Concerning the values that we see at the drop-down list, 1/1 is the default one, above it we seehigher values and below it we have the smaller ones.Lets say that we use as a prepass value the 4/1. In this case Thea will use frames 0, 1, 2 and 3 toaverage their GI to produce frame 0. The next step will be to take frame 1, 2, 3 and 4 to averageGI and produce frame 1 and so on, until producing all frames. With this procedure the finalrendered frames will be very consistent between each other (but the prepass level calculationtimes can be much bigger).

    Normally with a prepass level value at 1/1 we can have very smoothfinal results and small prepass calculation times. For increasing ordecreasing the prepass level value we need to take underconsideration the following parameters:- The Global Illumination settings (the parameters we have used forsetting up the Adaptive (BSD) engine). The higher the accuracy of thesettings we see at the Global Illumination panel, the fewer artifactswill be produced and the prepass level value of the walkthroughanimation can get lower values. If though, for making render timessmaller, we have used for example fewer samples or lower densityetc., we will need to increase the animation prepass level value toavoid flickering between frames or artifacts like black areas at someframes.- The speed of our animated camera (which is a very importantparameter). If we have a good GI solution and the camera movesrelative slow, then we can even use a prepass level of 1/5 or evenlower. This is possible because there are no abrupt changes betweenframes and Thea can calculate the missing samples easily. But if thecamera moves very fast, there will be many changes between framesand we cannot afford to exclude any frame from the prepasscalculation, because this will cause flickering problems at the renderedanimation. In this case we need to use at least a prepass level 1/1 (orhigher).

    Figure 6: GI Settings Panel

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  • At the next images we can see the way some animation frames look like for different prepass levelvalues.

    At the first set of images that follows we see a single frame rendered with prepass level 1/1 andthen the same frame rendered with prepass level 4/1. In both cases we have used the exact sameGlobal Illumination settings, and we see that the frame rendered with prepass 4/1 is smootherand better then the frame rendered with pre pass 1/1 (differences are not easily seen by firstobservation, but can be seen by a closer look).

    Figure 7: a single frame rendered with prepasslevel 1/1

    Figure 8: the same frame rendered with prepasslevel 4/1

    At the next set of images we see 2 frames showing the artifacts that can occur when we use a toolow prepass level like 1/5 or 1/10 with a very fast camera movement. As we have said, using apre pass level 1/1 is good for most walkthrough animations and depending on the speed of thecamera movement we may use higher prepass levels or lower, if the camera moves very slowly.

    Figure 9: frame rendered with prepass level 1/5while camera moves very fast

    Figure 10: frame rendered with a prepass level 1/10 with a very fast camera movement

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  • After making these necessary settings we can go at the Darkroom and start rendering the framessequence that will produce our animation.Note that when the walkthrough animation option is enabled, Thea will calculate at first thewhole irradiance pass of all the animation frames and after that it will ray trace the frames one byone. Please keep in mind that even if the irradiance computation for one frame can take quitemuch time (10 minutes for example) this is not an issue for the walkthrough animation, as at thenext frame, only some samples will be added to the irradiance calculation and so, in the end thetotal irradiance cache calculation will not take as much time as the ray tracing actually takes. Thismeans that as each frame needs to get fully ray traced, for reducing the total render times weneed to focus more on ray tracing settings rather than decreasing the Global illumination settingsand/or prepass level values.

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