Texture mapping originally referred to a method (now more accurately called diffuse mapping) that simply wrapped and mapped pixels from a texture to a 3D surface. In recent decades the advent of multi-pass rendering and complex mapping such as height mapping, bump mapping, normal mapping, displacement mapping, reflection mapping, specular mapping, mipmaps, occlusion mapping, and many other variations on the technique (controlled by a materials system) have made it possible to simulate near-photorealism in real time by vastly reducing the number of polygons and lighting calculations needed to construct a realistic and functional 3D scene.
“Creating everything from scratch is nice, but sometimes you’ve got to get things done fast and often times it’s just faster to use a photograph as a way to add real-world detail to your textures. If you’re taking your own photos for textures, make sure your images are as flat as possible.
Most 3D scenes will have lighting added to them later, so if you have lighting baked into the textures it can break the illusion of reality. For example, if you have a texture with a shadow being cast on the right side of the objects in the texture but your 3D scene has a light on the right side, the viewer’s eye will know something isn’t quite right because shadows shouldn’t be cast on the same side as the light source. For that reason it’s a good idea to bring your textures into Photoshop to remove any sort of lighting or shadows in the image if possible.
It’s worth pointing out that a lot of games do have baked lighting as a technique for faking the lighting. This is done intentionally, but it’s usually done a little later in the pipeline than the creation of the initial textures. Generally speaking you’ll want to remove any existing lighting from raw images.
You can learn more about projection painting in Texture Projection Techniques in MARI.”
“When you’ve got large surfaces to texture, it’s often necessary to create the map from just a small texture. For instance, if you need to texture an entire parking lot but you’ve only got a photo of a small portion of asphalt from your driveway then once that small texture is applied to the large area it’ll look distorted.
Instead, what you can do is to repeat, or tile, the smaller texture across the geometry. The catch to this is that tiling can cause visible seams if you’re not careful. To avoid this, most texturing programs have tools that let you repeat the edge pixels. By doing this you can create a new image that will tile seamlessly across your entire surface and avoid any visible seams.
You can learn more about tiling textures in Creating Seamless Textures for Games.”