Further, for a quad to be "planar", not only did it need to be geometrically flat but the texture coordinates also had to be 'flat'. IIRC the driver tried to detect if two consecutive triangles actually formed a planar quad and then replaced them with a more efficient representation. Squares have 90 degree angles / equilateral triangles have 60 degree angles. Having said all this, the original Series 1 PowerVR graphics chips (eg PCX1 and PCX2) used a lower-level primitive (the half plane) from which N-sided convex polygons ( or in fact N-sided polyhedra - e.g an entire cube was, at most, 6 half-planes) could be constructed. Differences: Squares have 4 sides / equilateral triangles have 3 sides. There is thus little point in adding additional hardware to support 'fast' quad rendering as (a) it wouldn't get used much and (b) is extremely unlikely to be the bottleneck in rendering! Making two triangles from a quad on the way down is easy. Quads may be the native higher surface element and even the way the data is stored but on the way to the gfx card its going to be almost always triangles. If you are concerned about the 'cost' in vertices of supplying two triangles to represent your quad, remember that APIs (and HW) have triangle strips/fans/indexed representations which will, in most cases, eliminate the additional vertex overheads. File formats intended for the fastest throughout of the video card ultimately break any higher level prinatives down to triangles. Playmetric Logo 3d cube design geometric hexagon impossible object logo logomark mark optical illusion. Neither seems, to me at least, as particularly attractive]. Discover 1 Triangle Button design on Dribbble. either collapse an edge by repeating a vertex or (but this may have other problems due to precision) making 3 of the vertices collinear or b) Using a degenerate quad to create a triangle - i.e. with a photo triangle the page 3D are edges from corner foam not of measuring the again. You need to be careful, though, not to introduce T-Junctions. [ Update: As pointed out, you could still use quads by either a) Noting that any triangle can be represented as 3 quads by the addition of four more vertices - one at the centre of the triangle and one on each edge). Scan converting/filling convex polygons is far simpler than a general polygon filling algorithmĪn arbitrary polygonal mesh can always be easily decomposed into triangles depth, texture coordinate, shading) can only take a 'single' value. This is also means that when scan converting a triangle, for each pixel, each attribute (e.g. This means that an individual single triangle cannot obscure itself (in terms of hidden surface removal) and thus cannot form an internal silhouette edge (when being rendered) nor, say, cast a shadow on itself. (Non-degenerate) triangles are guaranteed to be planar.There are several reasons for using triangles as the basic primitive.
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