identifying polygons

http://my.oschina.net/sweetdark/blog/161002Learning the knowledge of drawing lines, we can use Gl_line_loop to draw closed polygons. But in this way, only the wireframe is drawn, and the polygon has no fill color. OpenGL supports drawing a solid polygon and fills it with the current color.TriangleFor a simple triangle, you need to specify three vertices. 1:glbegin (Gl_triangles); 2: glvertex2f (0.0f, 0.0f); V0 3: glvertex2f (2

A General Polygon Clipping Library Version 2.32 http://www.cs.man.ac.uk/~toby/alan/software/gpc.html Alan Murta Advanced Interfaces Group Department of the computer science University of Manchester Manchester M13 9PL, UK Abstract:this document describes a C library implementation of a new polygon clipping algorithm. The techniques used is descended from Vatti ' s polygon clipping method [1]. Subject and clip polygons may is con

display list too many times, and the other is to spend too much time on the view hierarchy and unnecessary repainting, for two reasons the CPU is overworked when updating the display list or other cache GPU resources. 　　on the GPU side , the most common problem is what we're talking about: over-Drawing (Overdraw), which is often a waste of GPU processing time during pixel shading, when it's later shaded with other tools.Before the CPU draws an image on the screen, it enters the specified set of

"How many pointsDraw to the same pixel.In the same way, the math line has no width, but OpenGL's line is wide. Also, OpenGL's line must be a finite lengthdegrees, not as infinite as the mathematical concept. It can be argued that OpenGL's "straight line" concept is similar to the mathematically "line segment", which can beTwo endpoints to determine.A polygon is a closed area formed by the end-to-end of multiple segments. OpenGL stipulates that a polygon must be a "convex polygon" (itsRighteousn

the polygonThe 3,p is not on the edge of the polygon, but the ray of P is coincident with an edge of the polygon, such as coincident with the pi,pi+1 segment, if Pi-1 and pi+2 are on either side of the ray, this is an intersection, otherwise this situation does not count as the intersection. Similar to a situation, draw a picture should understand!By the way, the point in the plane of the figure of the judgmentA planar graph is composed of M polygons

rectangle. For the standard Cartesian plane, a commonMethod is to store the coordinates of the bottom-left and top-rightCorners. Suppose we have two rectangles R1 and R2. Let (x1, y1) beLocation of the bottom-left corner of R1 and (x2, y2) be the locationOf its top-right corner. Similarly, let (x3, y3) and (x4, y4) beRespective corner locations for R2. The intersection of R1 and R2 willBe a rectangle R3 whose bottom-left corner is at (max (x1, x3), max (y1,Y3) and top-right corner at (min (x2,

. As shown, draw a ray along the x-axis from that point, in order to determine the intersection of the Ray and each edge, and count the number of intersections, if the number of intersections is odd, then within the Polygon (3 intersection), if the focal number is even, then outside, the ray method for convex and non-convex polygon, the complexity is O (n), the other N is the number of sides. Source can be referenced (http://alienryderflex.com/polygon/)Figure 2 X-ray method to determine the poin

First, DirectoryThe basic concepts of computational geometry and common algorithms in this paper include the following:1. The concept of vectors2. Vector addition and subtraction3. Vector Cross Product4. The turn judgment of the broken line5. Determine if the point is on a line segment6. Determine if two segments intersect7. Determine if line segments and lines intersect8. Determine if the rectangle contains points9. Determine if line segments, polylines, and

, or it can be stopped when the depth of the BSP Tree exceeds a certain boundary. PseudocodeStruct bsp_tree{Plane partition;List polygons;Bsp_tree * front, * back;}; This struct definition will be used all the time in the following discussions. It indicates a contact of the BSP Tree, including a split plane, a list of polygon in the split plane, and a pointer to the child contact. Void buld_bsp_tree (bsp_tree * tree, list

A simple method for detecting a convex polygon collision is the SAT (separating axis theorem), the separation axis theorem .Principle: The polygon is projected onto a vector to see whether the projections of the two polygons overlap. If they do not overlap, the two polygons are considered separate, otherwise a vector is found to continue the projection. We don't need to compare a lot of vectors, because it'

Movement modification Axtewindow control keyboard shortcuts "0012 (Intermediate)" File operation--How to block Ctrl+o shortcut keys "0012 (Intermediate)" File operation--event allows you to do more "0020 (Intermediate)" Three-dimensional World modeling (point)--Dynamic Add model "0020 (Intermediate)" Three-dimensional World modeling (point)--dynamic addition of video projection "0025 (Intermediate)" Three-dimensional World modeling (line)--dynamic creation of line objects Spat

　　What are 3D polygon features?A polygon feature is a GIS object whose geographic representation (a series of x-and y-coordinate pairs for enclosing areas) is stored in a row of the database as one of its properties (or fields). Polygon features have two separate parts that may be used for modeling in 3D mode: their outer perimeter lines and inner areas. In almost all instances, polygons should be modeled as 3D features only if the outer perimeter nee

onto this axis. (Record this polygon projected to the highest and lowest point on the axis)Step Three: do the same with the second polygon.Step four: get the projection of these two polygons separately, and detect whether the two projections overlap.If you find a gap between these two projections to the "shadow" on the axis, then these two graphs must not intersect. But if there are no gaps, then they may be in contact, and you need to continue testi

; return dx*dx+dy*dyDr;};Convex polygon bounding box algorithm: for 2 polygons, to detect if they intersect, all we have to do is calculate the distance of each edge of two polygons on the split axis. Find out the maximum and minimum values of the vectors formed by each edge on the axis, so that each polygon on the split axis forms a segment with these two values, and finally compares whether the tw

1. Identifying Relationship:1 to many. The primary key of the parent entity is the foreign key (FK1) of the child entity, and FK1 is the primary key. 2. No identifying, mandatory relationship:1 to many. The primary key of the parent entity is the foreign key (FK1) of the child entity, and the FK1 is not empty. 3. No identifying, optional relaotionship:1 to many.

ring, press D Elete Delete, select the 3 extrudedsurface, click the Modify>convert nurbs to polygons option box in the main menu, and select Control in Tesselation method points , click Tesselate. Select 3 extrudedsurface in the Outliner panel, press DELETE to delete, and now only polygon objects are left in the scene. Maya Woven Fabric Modeling (Fig 8) 8. Select the three polygon objects, execute the

are linked: the edges of all triangles are notCan intersect with a different triangle. The result is a net covering the grid area, which is spliced together by triangles. Each triangle defines a polygon that covers the mesh nodes of the triangle. The triangle's tilt and elevation are defined by this triangleThree raw data points are determined. All nodes within a given triangle are constrained by the surface of the triangle. Because the original data pointare used to define the various triangle

{ returnX_multi (Seg.s, SEG.E, p) EPS;}BOOLInside (segment seg, point P)//determine if the point is inside the line, strictly inside, not including the boundary{ returnX_multi (Seg.s, SEG.E, p) >EPS;} Point Get_intersection (Point P1, point P2, point P3, point P4)//get the intersection of P1P2 and p3p4 of two straight lines{ DoubleA1, B1, C1, A2, B2, C2; Point TMP; A1= (P2.Y-p1.y); B1= (p1.x-p2.x); C1= (p2.x * p1.y-p1.x *p2.y); A2= (P4.Y-p3.y); B2= (p3.x-p4.x); C2= (P3.Y * P4.X-P4.Y

　　What is a multipatch feature?A multipatch feature is a GIS object that stores a collection of polygons that can represent the boundaries of a 3D object as a single row in a database. Polygons store texture, color, transparency, and geometry information that represents part of a feature. The geometry information stored in polygons can be triangles, triangular fa

I checked the information carefully. Some people have summarized the division of polygon through the Internet. Although OpenGL glutesselation is easy to use, it is said that the algorithm is not efficient. The better algorithm is the ploy2tri algorithm. Try again if you have time.Triangulation of simple polygons Ben discoe, notes from 2001.02.11, updated through 2009.01 I needed some code for tessellating polygons