Posted February 27, Why is this hard limit still not "upgraded" in VW? Brendan Gray Posted July 6, Posted July 6, Charlie Winter Posted July 27, Posted July 27, Posted July 28, Huug Posted July 28, I hope that at some point a decent real time rendering engine wil be implemented in VW.
In its hard to impress a client with the clunky VW web viewer. Posted May 11, TonyBalogna Posted November 24, Posted November 24, Join the conversation You can post now and register later. More than 8 lights? I hope someone could tell me more about how to do this. Thanks, Dennis. Thanks for all quick responses. Alluded to above, but some references: lightmaps Unfortunately lightmaps lead directly into the task of building and understanding a world editor, no mean feat.
Abstracting this functionality away in a function like this has the advantage that we can easily calculate the lighting for multiple point lights without the need for duplicated code. In the main function we simply create a loop that iterates over the point light array that calls CalcPointLight for each point light. Now that we defined both a function for directional lights and a function for point lights we can put it all together in the main function.
Each light type adds its contribution to the resulting output color until all light sources are processed. The resulting color contains the color impact of all the light sources in the scene combined. We leave the CalcSpotLight function as an exercise for the reader.
Setting the uniforms for the directional light struct shouldn't be too unfamiliar, but you may be wondering how to set the uniform values of the point lights since the point light uniform is actually an array of PointLight structs.
This isn't something we've discussed before. Luckily for us, it isn't too complicated. Setting the uniform values of an array of structs works just like setting the uniforms of a single struct, although this time we also have to define the appropriate index when querying the uniform's location:. Here we index the first PointLight struct in the pointLights array and internally retrieve the location of its constant variable, which we set to 1.
Let's not forget that we also need to define a position vector for each of the 4 point lights so let's spread them up a bit around the scene. We'll define another glm::vec3 array that contains the pointlights' positions:. Then we index the corresponding PointLight struct from the pointLights array and set its position attribute as one of the positions we just defined. Also be sure to now draw 4 light cubes instead of just 1.
Simply create a different model matrix for each of the light objects just like we did with the containers. If you'd also use a flashlight, the result of all the combined lights looks something like this:. The OpenGL lighting equations are just an approximation but one that works fairly well and can be computed relatively quickly. If you desire a more accurate or just different lighting model, you have to do your own calculations in software.
Such software can be enormously complex, as a few hours of reading any optics textbook should convince you. In the OpenGL lighting model, the light in a scene comes from several light sources that can be individually turned on and off. Some light comes from a particular direction or position, and some light is generally scattered about the scene. For example, when you turn on a light bulb in a room, most of the light comes from the bulb, but some light comes after bouncing off one, two, three, or more walls.
This bounced light called ambient is assumed to be so scattered that there is no way to tell its original direction, but it disappears if a particular light source is turned off. Finally, there might be a general ambient light in the scene that comes from no particular source, as if it had been scattered so many times that its original source is impossible to determine. In the OpenGL model, the light sources have an effect only when there are surfaces that absorb and reflect light.
Each surface is assumed to be composed of a material with various properties. A material might emit its own light like headlights on an automobile , it might scatter some incoming light in all directions, and it might reflect some portion of the incoming light in a preferential direction like a mirror or other shiny surface.
The OpenGL lighting model considers the lighting to be divided into four independent components: emissive, ambient, diffuse, and specular. All four components are computed independently and then added together. A mbient illumination is light that's been scattered so much by the environment that its direction is impossible to determine - it seems to come from all directions.
Backlighting in a room has a large ambient component, since most of the light that reaches your eye has first bounced off many surfaces. A spotlight outdoors has a tiny ambient component; most of the light travels in the same direction, and since you're outdoors, very little of the light reaches your eye after bouncing off other objects.
When ambient light strikes a surface, it's scattered equally in all directions. The diffuse component is the light that comes from one direction, so it's brighter if it comes squarely down on a surface than if it barely glances off the surface.
Once it hits a surface, however, it's scattered equally in all directions, so it appears equally bright, no matter where the eye is located. Any light coming from a particular position or direction probably has a diffuse component. Finally, specular light comes from a particular direction, and it tends to bounce off the surface in a preferred direction. A well-collimated laser beam bouncing off a high-quality mirror produces almost percent specular reflection. Shiny metal or plastic has a high specular component, and chalk or carpet has almost none.
You can think of specularity as shininess. Although a light source delivers a single distribution of frequencies, the ambient, diffuse, and specular components might be different. For example, if you have a white light in a room with red walls, the scattered light tends to be red, although the light directly striking objects is white. OpenGL allows you to set the red, green, and blue values for each component of light independently. The OpenGL lighting model makes the approximation that a material's color depends on the percentages of the incoming red, green, and blue light it reflects.
For example, a perfectly red ball reflects all the incoming red light and absorbs all the green and blue light that strikes it. If you view such a ball in white light composed of equal amounts of red, green, and blue light , all the red is reflected, and you see a red ball.
If the ball is viewed in pure red light, it also appears to be red. If, however, the red ball is viewed in pure green light, it appears black all the green is absorbed, and there's no incoming red, so no light is reflected. Like lights, materials have different ambient, diffuse, and specular colors, which determine the ambient, diffuse, and specular reflectances of the material.
A material's ambient reflectance is combined with the ambient component of each incoming light source, the diffuse reflectance with the light's diffuse component, and similarly for the specular reflectance and component.
Ambient and diffuse reflectances define the color of the material and are typically similar if not identical. Specular reflectance is usually white or gray, so that specular highlights end up being the color of the light source's specular intensity.
If you think of a white light shining on a shiny red plastic sphere, most of the sphere appears red, but the shiny highlight is white. In addition to ambient, diffuse, and specular colors, materials have an emissive color, which simulates light originating from an object.
In the OpenGL lighting model, the emissive color of a surface adds intensity to the object, but is unaffected by any light sources. Also, the emissive color does not introduce any additional light into the overall scene. The color components specified for lights mean something different than for materials.
For a light, the numbers correspond to a percentage of full intensity for each color. If the R, G, and B values for a light's color are all 1. If the values are 0. For materials, the numbers correspond to the reflected proportions of those colors. If any of the sums are greater than 1 corresponding to a color brighter than the equipment can display , the component is clamped to 1. Define normal vectors for each vertex of all the objects.
These normals determine the orientation of the object relative to the light sources. Create and select a lighting model , which defines the level of global ambient light and the effective location of the viewpoint for the purposes of lighting calculations. Example accomplishes these tasks.
It displays a sphere illuminated by a single light source, as shown earlier in Figure The lighting-related calls are in the init command; they're discussed briefly in the following paragraphs and in more detail later in the chapter. The OpenGL lighting calculation is different for the two modes, and in fact the lighting capabilities are more limited in color-index mode. Thus, RGBA is the preferred mode when doing lighting, and all the examples in this chapter use it.
See "Lighting in Color-Index Mode" for more information about lighting in color-index mode. An object's normals determine its orientation relative to the light sources. For each vertex, OpenGL uses the assigned normal to determine how much light that particular vertex receives from each light source. In this example, the normals for the sphere are defined as part of the glutSolidSphere routine. See "Normal Vectors" in Chapter 2 for more details on how to define normals.
Example uses only one, white light source; its location is specified by the glLightfv call. You can include at least eight different light sources in your scene of various colors; the default color of these other lights is black.
The particular implementation of OpenGL you're using might allow more than eight. You can also locate the lights wherever you desire - you can position them near the scene, as a desk lamp would be, or an infinite distance away, like the sun. In addition, you can control whether a light produces a narrow, focused beam or a wider beam. Remember that each light source adds significantly to the calculations needed to render the scene, so performance is affected by the number of lights in the scene.
See "Creating Light Sources" for more information about how to create lights with the desired characteristics. After you've defined the characteristics of the lights you want, you have to turn them on with the glEnable command. See "Enabling Lighting" for more information.
In Example , the only element of the lighting model that's defined explicitly is the global ambient light. The lighting model also defines whether the viewer of the scene should be considered to be an infinite distance away or local to the scene, and whether lighting calculations should be performed differently for the front and back surfaces of objects in the scene. Example uses the default settings for these two aspects of the model - an infinite viewer and one-sided lighting.
Using a local viewer adds significantly to the complexity of the calculations that must be performed, because OpenGL must calculate the angle between the viewpoint and each object. With an infinite viewer, however, the angle is ignored, and the results are slightly less realistic.
Further, since in this example, the back surface of the sphere is never seen it's the inside of the sphere , one-sided lighting is sufficient. An object's material properties determine how it reflects light and therefore what material it seems to be made of.
Because the interaction between an object's material surface and incident light is complex, specifying material properties so that an object has a certain desired appearance is an art. You can specify a material's ambient, diffuse, and specular colors and how shiny it is. In this example, only these last two material properties - the specular material color and shininess - are explicitly specified with the glMaterialfv calls.
See "Defining Material Properties" for a description and examples of all the material-property parameters. As you write your own lighting program, remember that you can use the default values for some lighting parameters; others need to be changed.
Also, don't forget to enable whatever lights you define and to enable lighting calculations. Finally, remember that you might be able to use display lists to maximize efficiency as you change lighting conditions. Light sources have a number of properties, such as color, position, and direction. The following sections explain how to control these properties and what the resulting light looks like. For other lights, the default value is 0.
As you can see, arrays are defined for the parameter values, and glLightfv is called repeatedly to set the various parameters. Note: Remember to turn on each light with glEnable. See "Enabling Lighting" for more information about how to do this. These parameters interact with those that define the overall lighting model for a particular scene and an object's material properties.
This value was used in Example If this program had specified blue ambient light as. Typically, a real-world object such as a glass bottle has a specular highlight that's the color of the light shining on it which is often white.
Note: The alpha component of these colors is not used until blending is enabled. See Chapter 6. Until then, the alpha value can be safely ignored. As previously mentioned, you can choose whether to have a light source that's treated as though it's located infinitely far away from the scene or one that's nearer to the scene.
The first type is referred to as a directional light source; the effect of an infinite location is that the rays of light can be considered parallel by the time they reach an object. An example of a real-world directional light source is the sun. The second type is called a positional light source, since its exact position within the scene determines the effect it has on a scene and, specifically, the direction from which the light rays come.
A desk lamp is an example of a positional light source.
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