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Global Illumination (GI) is the technique in computer graphics that replicates realistic lighting interactions. It calculates not only the direct lighting from a source but also the indirect lighting that reaches a surface after multiple bounces.<\/p>\n\n\n\n
In the real world, light continues to bounce off surfaces until its energy dissipates. Simulating this phenomenon is crucial for producing renderings with realistic brightness, contrast, and detail.<\/p>\n\n\n\n GI aims to solve the problem of light bouncing in the scene twice and afterwards, which can bring better brightness and detail to the parts that are not illuminated by direct lighting. It plays a crucial role in creating photorealistic renderings that can trick the human eye.<\/p>\n\n\n\n Given its importance, GI has been a persistent technical challenge in the rendering industry. Over the years, various solutions, including ray tracing, have been developed to implement GI effectively. However, achieving real-time GI is particularly difficult due to the limited computational time available.<\/p>\n\n\n\n Real-time GI represents the forefront of rendering technology, offering immediate feedback and enabling seamless creative workflows. D5 Render <\/a>has tackled these challenges by developing an advanced GI solution that combines quality and speed.<\/p>\n\n\n\n The rendering equation, introduced by Kajiya, underpins GI algorithms. It models how light interacts with a scene, adhering to the laws of physics and energy conservation. Solving this equation in real-time (less than 0.03 seconds) is highly complex.<\/p>\n\n\n\n Previous real-time GI solutions have issues including light leakage, excessive occlusion and a lot of noise due to inadequate sampling rates.<\/p>\n\n\n\n D5 Render <\/a>overcame these limitations with a groundbreaking approach called ReSTIR Surfel GI<\/strong>, which delivers high-quality results at real-time speeds.<\/p>\n\n\n\n D5<\/a> uses ReSTIR on GI to store the paths of rays rather than sampling light sources. ReSTIR GI reduces the variance of the sampling results by reusing sample information between frames and between neighboring pixels, allowing it to achieve high-quality results even when there’re only a small number of samples.<\/p>\n\n\n\n D5 Render <\/a>applies ReSTIR to GI by:- Storing ray paths rather than sampling light sources directly.- Minimizing temporal lag with Path Validation<\/strong>, which adjusts reused samples when brightness or object positions change dynamically.<\/p>\n\n\n\n While ReSTIR excels at initial bounces, subsequent bounce calculations present additional challenges. Therefore, the D5 GI solution applied a Surfel Caching solution for subsequent bounce calculations.<\/p>\n\n\n\n Surfel is a spatial caching technique that can be iteratively generated based on screen space and efficiently accumulate and cache irradiance, allowing GI rays to simply query the lighting results for subsequent bounces. However, this solution introduces some new problems, such as being unable to obtain results outside of the screen space.<\/p>\n\n\n\n To address this issue, D5<\/a> made improvements to the Surfel Caching solution. It generates Surfel from the intersection of the ray emitted by GBuffer, storing the Surfel of the location outside the view and thus obtaining the correct result.<\/p>\n\n\n\n Besides, the scene is divided into cascadinBesides, the scene is divided into cascading Grids to manage Surfels and thus reduce VRAM usage. Light leakage is solved by sorting and comparing the times of ray bounces. Other artifacts are also improved.g Grids to manage Surfels and thus reduce VRAM usage. Light leakage is solved by sorting and comparing the times of ray bounces. Other artifacts are also improved.<\/p>\n\n\n\n En D5<\/a> Team has also developed a series of solutions for multiple light source sampling, reflection, and denoise, allowing the ReSTIR Surfel GI to function efficiently and reliably in various scenarios.<\/p>\n\n\n\n The D5 GI solution has been significantly enhanced to incorporate skylight into both primary and secondary GI bounces, resulting in realistic lighting even in spaces with substantial depth.<\/p>\n\n\n\n This improvement ensures brighter interiors with smooth transitions between light and shadow. GI calculations now use local texture colors directly, providing more accurate color transitions and enhancing the realism of indirect lighting and reflections. These updates eliminate the overly brightened look of previous versions while achieving realistic color differentiation. Users seeking controlled saturation can enable the “Limit Color Bleeding<\/strong><\/a>” option.<\/p>\n\n\n\n In the older version, interior lighting appeared warmer and metals darker.<\/em><\/p>\n\n\n\n The updated version has neutral color temperature and brighter metals.<\/em><\/p>\n\n\n\n The newest version<\/strong><\/a> features higher GI sampling accuracy, delivering better contrast in backlit areas, clearer bounce lighting, and more defined occlusion shadows in crevices. These refinements bring lighting effects closer to real-life expectations, improving both subtle and high-contrast scenarios.<\/p>\n\n\n\n Previous versions prioritized strong denoising, leading to flat images. The new GI solution integrates NVIDIA’s real-time denoiser and low-variance Restir sampling, offering sharper high-frequency shadow details. Additionally, soft shadows from multiple light sources in reflections\u2014previously limited to still images\u2014are now available for video rendering. While not visible in real-time previews, these shadows are correctly calculated in final outputs, enhancing realism.<\/p>\n\n\n\n The new\u00a0D5<\/a>\u00a0GI solution and skylight simulation realistically replicate the semi-transparency of leaves when illuminated, enhancing the natural appearance of plants.\u00a0D5 updated version<\/strong><\/a>\u00a0improved GI sampling and brightness deliver lighting effects that closely mirror real-life conditions, eliminating the overly brightened look of previous versions.<\/p>\n\n\n\n Earlier versions calculated only the direct lighting of emissive materials, rendering them unsuitable as main light sources.\u00a0On D5 latest version<\/strong><\/a>, the GI solution calculates light bounces, enabling emissive materials to perform more effectively as light sources.<\/p>\n\n\n\n The new version introduces a Light Grid structure, raising the artificial light source limit from 1,024 to 4,096. This improves light sampling efficiency without impacting older archives.<\/p>\n\n\n\n Thanks to Light Grid technology, direct lighting is now more stable in scenes with multiple light sources, intense brightness, and complex occlusions, reducing flickering and ensuring smoother video rendering, particularly for plants in night scenes.<\/p>\n\n\n\n![\"\"](\"https:\/\/usa-wps.d5render.com\/wp-content\/uploads\/2026\/03\/image-159-1024x316.png\")
1.2 Why real-time GI?<\/h3>\n\n\n\n
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02 The logic behind D5 GI solution<\/h2>\n\n\n\n
2.1 Previous solutions<\/h3>\n\n\n\n
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2.2 ReSTIR Surfel GI<\/strong><\/h3>\n\n\n\n
2.2.1 ReSTIR GI<\/strong><\/h4>\n\n\n\n
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2.2.2 Surfel GI<\/strong><\/h4>\n\n\n\n
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2.2.3 Other optimisations<\/strong><\/h4>\n\n\n\n
03 Improved Global Illumination (GI) for Realistic Rendering<\/h2>\n\n\n\n
3.1 Enhanced Interior Illumination and Color Rendering<\/h3>\n\n\n\n
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<\/figure>\n\n\n\n3.2 Realistic Contrast, Shadows, and Color Rendering<\/strong><\/h3>\n\n\n\n
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<\/figure>\n\n\n\n3.3 High-Frequency Shadow Details and Soft Shadows<\/strong><\/h3>\n\n\n\n
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04 Realism Enhancements Across Materials and Textures<\/h2>\n\n\n\n
4.1 Improved Plant Rendering<\/strong><\/h3>\n\n\n\n
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<\/figure>\n\n\n\n4.2 Emissive Materials as Light Sources<\/strong><\/h3>\n\n\n\n
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05 Enhanced Light Management and Rendering Efficiency<\/h2>\n\n\n\n
5.1 Increased Light Source Capacity<\/strong><\/h3>\n\n\n\n
5.2 Reduced Flickering in Video Rendering<\/strong><\/h3>\n\n\n\n
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