User Tools
Differences
This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision Next revision | Previous revision | ||
|
mapping:cawe:lighting [2007-10-23 23:01] Carsten |
mapping:cawe:lighting [2013-01-07 12:07] (current) |
||
|---|---|---|---|
| Line 1: | Line 1: | ||
| ====== About Lights and Shadows ====== | ====== About Lights and Shadows ====== | ||
| - | FIXME This page is currently under construction :!: | + | FIXME This page is still under construction :!: |
| One of the key questions that mappers frequently raise is how to define and place light sources. | One of the key questions that mappers frequently raise is how to define and place light sources. | ||
| - | While placing light sources is generally easy, this section explains the types of available lighting techniques in Ca3DE and the options to create light sources for each. | + | While placing light sources is generally easy, this section explains the types of available lighting techniques in Cafu and the options to create light sources for each. |
| - | The Ca3D-Engine implements two different types of lighting techniques: | + | The Cafu engine implements two different types of lighting techniques: |
| * Radiosity-based lighting and | * Radiosity-based lighting and | ||
| * dynamic lighting. | * dynamic lighting. | ||
| - | The two lighting techniques are quite distinct from each other, and each comes with a set of feature of its own. Nonetheless, both techniques peacefully coexist in the Ca3D-Engine and mappers frequently employ both in a single map. | + | The two lighting techniques are quite distinct from each other, and each comes with a set of feature of its own. Nonetheless, both techniques peacefully coexist in the Cafu engine and mappers frequently employ both in a single map. |
| Line 18: | Line 18: | ||
| Radiosity methods compute lighting based on a physical model, and it is the nature of the underlying mathematics that characterizes the features of the technique. | Radiosity methods compute lighting based on a physical model, and it is the nature of the underlying mathematics that characterizes the features of the technique. | ||
| - | The big downside of Radiosity is that it requires a preprocessing step. This preprocessing step can be computationally very expensive and thus taking a long time to complete. It is implemented in a special tool called "CaLight", which is one of the map compilers that are covered in sections [[mapping:compiling_new]] and [[mapping:compiling]]. | + | The big downside of Radiosity is that it requires a preprocessing step. This preprocessing step can be computationally very expensive and thus take a long time to complete. It is implemented in a special tool called "CaLight", which is one of the map compilers that are covered in sections [[mapping:compiling_new]] and [[mapping:compiling]]. |
| The fact that Radiosity is slow to precompute also means that it cannot work with dynamic objects: Radiosity takes walls and any other static object into account, but anything that moves will not influence the Radiosity-based lighting result. | The fact that Radiosity is slow to precompute also means that it cannot work with dynamic objects: Radiosity takes walls and any other static object into account, but anything that moves will not influence the Radiosity-based lighting result. | ||
| Line 24: | Line 24: | ||
| Good news about Radiosity-based lighting is that once the preprocessing step it complete, it is //fast//. Independently of the number of light sources or complexity of the scene, Radiosity-based lighting provides very good performance at run-time during the game. It is therefore a natural choice for large-scale base lighting of any level. | Good news about Radiosity-based lighting is that once the preprocessing step it complete, it is //fast//. Independently of the number of light sources or complexity of the scene, Radiosity-based lighting provides very good performance at run-time during the game. It is therefore a natural choice for large-scale base lighting of any level. | ||
| - | Even better, Radiosity lighting results looks stunningly good. No matter what hardware vendors tell you about their latest products, no matter what game developers tell you about dynamic lighting (as I too do, see below), none of these techniques can beat the realism of lighting generated by Radiosity methods. Based on an accurate physical model, the natural propagation and appearance of lights and shadows is unique to Radiosity methods. | + | Even better, Radiosity lighting results looks stunningly good. No matter what hardware vendors tell you about their latest products, no matter what game developers tell you about dynamic lighting (as I do, too; see below), none of these techniques can beat the realism of lighting generated by Radiosity methods. Based on an accurate physical model, the natural propagation and appearance of lights and shadows is unique to Radiosity methods. |
| - | For these reasons, Radiosity was the first lighting technique implemented in Ca3DE. | + | The Radiosity method also handles //area light sources// without special measures, but as a natural part of the algorithm. Area light sources are an important key feature, because they are the main contributors to a realistic lights and shadows distribution with diffuse reflections and soft shadows. |
| + | This is contrary to dynamic lighting, where lights are only points in space, soft shadows are always the result of some kind of trick, diffuse reflections are not possible at all, and a physical model is never involved. | ||
| + | |||
| + | For these reasons, Radiosity was the first lighting technique implemented in Cafu. | ||
| Here is an overview of the available Radiosity light sources and how they are created in a map: | Here is an overview of the available Radiosity light sources and how they are created in a map: | ||
| - | - As Radiosity lights are true //area light sources//, you can turn any solid surface in a Ca3DE map into a Radiosity light. | ||
| - | - xx | ||
| - | - yy | ||
| - | * [ FIXME TODO: Screenshots!, link to my thesis in See Also section, link to DK project] | + | ==== Area Light Sources ==== |
| - | * Radiosity lights are **area** light sources. | + | Any primitive (brush or Bezier patch) surface that you place in a Cafu map can be turned into an //area light source//. The key point here is that a surfaces characteristic of being an area light source is //not// :!: directly set in the Cafu World Editor CaWE. Rather, being an area light source is a //material// property. |
| - | * (whose irradiance is defined with the material), | + | That means that a surface becomes an area light source when it has a material applied to it which in turn is defined to emit Radiosity light. |
| - | * radiosity point light source entities, | + | |
| - | * sky light. | + | * In order to place an area light source, use the [[mapping:cawe:editingtools:editfaceprops|Edit Surfaces]] tool to apply an appropriately defined material to the desired brush or Bezier patch surface. You can learn which materials cast Radiosity area light by clicking on them once in the [[mapping:cawe:materialbrowser|Material Browser]]. The bar at the bottom will show "Radiant Exitance" information on the selected material, if any.\\ Tip: Filter for materials with the string "light" in their name. This heightens the chance to find a relevant material quickly. |
| + | * In order to change the definition of a new or existing material to emit light, make sure that the ''meta_radiantExitance'' keyword is employed. Please refer to the Material Systems [[matsys:cmat_manual:keywordreference]] for more details.\\ Note that the effect of changing the definition of an //existing// material is //global//. That is, if the material is used elsewhere (in another map), also the other map will be affected when CaLight is run next. | ||
| + | |||
| + | |||
| + | ==== Point light sources ==== | ||
| + | You can also place //point light sources// to participate in the Radiosity lighting process. | ||
| + | This is easily achieved with the [[mapping:cawe:editingtools:newlight|New Light tool]], whose documentation explains the placement and parameter setup in detail. | ||
| + | |||
| + | |||
| + | ==== Sky Light ==== | ||
| + | Adding sun- or moonlight to a map works analogously to adding an area light source: Just apply a "sky" material to any surface, and if the material is defined to emit skylight, everything else will happen automatically: | ||
| + | |||
| + | * The [[mapping:cawe:materialbrowser|Material Browser]] browser informs you whenever a material with "Irradiance" values is selected. | ||
| + | * The material definition can be changed according to the Material Systems [[matsys:cmat_manual:keywordreference]], see the ''meta_sunlight'' keyword. | ||
| + | * You may refer to the [[mapping:cawe:yourfirstmap]] tutorial to see an example. It's actually that easy! | ||
| ===== Dynamic Lighting ===== | ===== Dynamic Lighting ===== | ||
| - | * hardware accelerated. | + | Dynamic lighting has become popular with the advent of hardware-acceleration for 3D graphics in the recent years. |
| - | * dynamic light+shadow entities | + | It is the preferred and most frequently employed lighting technique in most recent commercial graphics software. |
| + | |||
| + | The essential characteristic of dynamic lighting is that its computational steps occur //per-pixel// and //per-frame//. | ||
| + | //Per-pixel// means that the lighting computations occur on the basis of the output pixels of the rendered primitives (triangles). | ||
| + | //Per-frame// refers to the fact that all lighting computations occur only at runtime, and in fact, they are performed for each rendered frame anew. This allows both light sources and lit objects to move arbitrarily through the scene, with the lights and shadows being updated correctly and instantaneously. | ||
| + | |||
| + | These properties have many implications for the practical use of dynamic lighting: | ||
| + | Dynamic lighting is fast, flexible, dynamic, instantaneous, yields good results and is well supported and accelerated in hardware. | ||
| + | |||
| + | Even though dynamic lighting looks not quite as real as the Radiosity method, this is often not a problem, because lighting that looks dramatically good is often preferred over the "boring natural". Moreover, dynamic lighting avoids the computational complexity that comes with the Radiosity method. Therefore, dynamic lighting is an important component in Cafu. | ||
| + | |||
| + | ==== Point light sources ==== | ||
| + | ==== Projective lights ==== | ||
| + | ==== Stencil shadows ==== | ||
| + | ==== Shadow-Map shadows ==== | ||
| Line 51: | Line 79: | ||
| Lighting with [[wp>Spherical_harmonics|Spherical Harmonics]] ("SHL") is an area of active research in computer science. Its goal is to combine the merits of Radiosity-based lighting with light sources that can move, especially when the light sources are very far away from the scene, like for example the sun or the moon. | Lighting with [[wp>Spherical_harmonics|Spherical Harmonics]] ("SHL") is an area of active research in computer science. Its goal is to combine the merits of Radiosity-based lighting with light sources that can move, especially when the light sources are very far away from the scene, like for example the sun or the moon. | ||
| - | SHL has been implemented in the scope of my diploma thesis in the Ca3D-Engine, but is currently not supported by the public releases. You may refer to the thesis below for more information. | + | SHL has been implemented in the scope of my diploma thesis in the Cafu engine, but is currently not supported by the public releases. You may refer to the thesis linked below for more information. |
| ===== See Also ===== | ===== See Also ===== | ||
| - | * [[http://www.ca3d-engine.de/download.php?view.5|Methods for Real-Time Lighting]] -- Diploma Thesis by Carsten Fuchs. | + | * [[http://www.cafu.de/files/Uni-DA-RealTimeLighting.pdf|Methods for Real-Time Lighting]] -- Diploma (Masters) Thesis by Carsten Fuchs. |
mapping/cawe/lighting.1193173299.txt.gz · Last modified: 2013-01-07 12:07 (external edit)