VRay...

For the entire scene i have been using the newly released Vray 2.0, This renderer provides a realtime renderes that utilizes the full potential of my GPU. One of vrays key features appart from the realistic lighting solutions is the Vray physical camera, this is similar to any other virtual cam but has all of the settings of a real camera such as exposure time, vignetting and shutter angle weather it be for a still cam or a camcorder, analogue or digital.

When using a realistic renderer its easy to have render time of going into hours per frame especially when calculating global illumination for each frame and fine details so it is essential to have a good understanding of the renderer and general illumination settings.

For this project i had begin with a render time of 30minutes per fram and with each scene containing up to 1150 frames i would need about 1725 hours to render before post production, particle simulation and geometry caches. To reduce this time i had started with the illumination settings, this would reduce the lighting quality but preserve the overall look of the scene. Taking the z-depth into consideration most of the illumination wasn't necessary so for each shot I had analysed what was relevant to the final comp and began adapting.

The default Vray settings are modified to suit an indoor architectural scene but since my shots were all out doors i had altered the presets drastically. To start with the default settings combine an irradiance map with brute force GI and for my outdoor scene the addition of the brute force pass was completely unnecessary. Brute force GI calculations renders the scene using the Vray renderers core lighting algorithms and caches nothing, this solution is by far the most accurate when specified but at the highest price of render time and since my scene had no glass properties or extremely fine detail such as fur or hi-res HDRI's the brute orce approche was dismissed. For all of the scenes Vrays irradiance map was used, this approach creates a light map using rays from the camera and interpolates the illumination by blurring nearby samples so for an outdoor scene natural haze and dust a sharp crisp intior solution can be substituted for the irradiance map.

My settings for the first scene used and extremely low sampling rate of -3 / -4 since its a flat planar scene including have and dust but i had set the sub-sample divisions to a high value of 50 to separate the shadows of the grass. One problem with the irradiance map is that the samples are randomised (for best results) so for the finer details of a static objects, such at the grass, flickering can occur, to overcome this i rendered the map using the cameras entire path and localised the randomisation per sample so that in each frame each area would have the same rate of sub sampling. The second scene also uses a low sample rate but without any fine details the sub-sampling divisions was lowered to just 10 without a reduction in image quality. this was mainly due to the addition of motion blur with a look up rate of only 2 frames in either direction. The final shot included the main explosion, this explosion had an extremely low voxel value since it was made up of volumetric particles and these voxels both received and emitted vray GI as well as scattering them within the cloud so a high sampling rate was crucial to fully capture the lighting within the voxels. With a high rate of samples, 1 / 3 i had used a low sub-sample devision value of 10.

The scene is globally lit with the vray sky map which is linked to a vray sun node which illuminates the entire scene with even lighting but only produces 25000 photons which which are focused into a specific area. Using the light cache or the photon map GI solutions and caustics, refractive or reflective, could only be generated within the specified area as well as environmental effects such as fog or volumetric lighting. Thankfully though Vrays modified irradiance map works on real world intensity principles such as Lux and lumens so all GI effects can be rendered wherever the camera points. irradiance maps can also be generated without rendering or incrementally during rendering which save huge amounts of time hen rendering a static scene. For my scene however, with the volumetric effects the best results were from creating new light maps for each frame.