TESSELATION 1 OUTLINE Tessellation in OpenGL Tessellation of - PowerPoint PPT Presentation

TESSELATION 1

OUTLINE Tessellation in OpenGL • • Tessellation of Bezier Surfaces • Tessellation for Terrain/Height Maps Level of Detail • 2

THE PIPELINE • Remember the pipeline?

OPENGL PIPELINE • Tessellation is done in three pipeline stages: Tessellation Control Shader (TCS) • • Allows us to configure the types of triangles generated Tessellator • • Produces a fixed grid of triangles Tessellation Evaluation Shader (TES) • • Allows us to manipulate the grid TCS and TES are programmable • • Middle stage, tessellator, is not programmable

THE EXAMPLE

TESSELLATION LEVELS

VERTEX SHADER #version 430 uniform mat4 mvp; void main(void) { }

TESSELLATION CONTROL SHADER #version 430 uniform mat4 mvp; layout (vertices = 1) out; void main(void) { gl_TessLevelOuter[0] = 6; gl_TessLevelOuter[2] = 6; gl_TessLevelOuter[1] = 6; gl_TessLevelOuter[3] = 6; gl_TessLevelInner[0] = 12; gl_TessLevelInner[1] = 12; }

TESSELLATION EVALUATION SHADER #version 430 layout (quads, equal_spacing, ccw) in; uniform mat4 mvp; void main (void) { float u = gl_TessCoord.x; float v = gl_TessCoord.y; gl_Position = mvp * vec4(u,0,v,1); }

FRAGMENT SHADER #version 430 out vec4 color; uniform mat4 mvp; void main(void) { color = vec4(1.0, 1.0, 0.0, 1.0); }

TESSELLATION FOR BEZIER SURFACES

THE EXAMPLE

TESSELLATION FOR TERRAIN / HEIGHT MAPS

OVERLY JAGGED

HEIGHT MAP AND NORMAL MAP

WITH NORMAL MAP AND LIGHTING

LEVEL OF DETAIL

SUMMARY • Tessellation in OpenGL • Tessellation of Bezier Surfaces • Tessellation for Terrain/Height Maps • Level of Detail 19