OpenGL ES 2.0 Common Profile Specification v1.19: Differences & Implementation Details

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8 OpenGL Operation

2.10 Rectangles

The commands for directly specifying rectangles are not supported.

OpenGL 2.0

Common

void Rect{sifd}(T x1, T y1, T x2, T y2)

–

void Rect{sifd}v(T v1[2], T v2[2])

–

n The rectangle commands are not used enough in applications to justify maintaining a redundant

mechanism for drawing a rectangle. q

2.11 Coordinate Transformations

The ﬁxed function transformation pipeline is no longer supported. The application can compute the neces-

sary matrices (can be the combined modelview and projection matrix, or an array of matrices for skinning)

and load them as uniform variables in the vertex shader. The code to compute transformed vertex will now

be executed in the vertex shader.

The Viewport command is supported since the viewport transformation happens after the programmable

vertex transform and is a ﬁxed function.

OpenGL 2.0

Common

void DepthRange(clampd n, clampd f)

–

void DepthRangef(clampf n, clampf f)



void Viewport(int x, int y, sizei w, sizei h)



void MatrixMode(enum mode)

–

void LoadMatrixf(float m[16])

–

void LoadMatrixd(double m[16])

–

void MultMatrixf(float m[16])

–

void MultMatrixd(double m[16])

–

void LoadTransposeMatrix{fd}(T m[16])

–

void MultTransposeMatrix{fd}(T m[16])

–

void LoadIdentity(void)

–

void Rotatef(float angle, float x, float y, float z)

–

void Rotated(double angle, double x, double y, double

–

void Scalef(float x, float y, float z)

–

void Scaled(double x, double y, double z)

–

void Translatef(float x, float y, float z)

–

void Translated(double x, double y, double z)

–

void Frustum(double l, double r, double b, double t,

double n, double f)

–

void Ortho(double l, double r, double b, double t,

double n, double f)

–

void Frustumf(float l, float r, float b, float t, float

n, float f)

–

10 OpenGL Operation

2.12 Clipping

Clipping against the viewing frustum is supported; however, separate user-speciﬁed clipping planes are not

supported.

The following modiﬁcations describes how lines and points are clipped in OpenGL ES 2.0

If the primitive is a point, then clipping discards it if it lies outside the near or far clip plane; otherwise,

it is passed unchanged. If the primitive is a line segment, and a part of it lies outside the space between the

near and the far plane, the line is clipped and new vertex coordinates are computed for one or both vertices.

A clipped line segment endpoint lies on both the original line segment and on either the near or the far

clipping plane. If the line segment lies completely between the two planes, it is passed unchanged.

OpenGL 2.0

Common

void ClipPlane(enum plane, const double

equation)

–

void GetClipPlane(enum plane, double

equation)

–

void Enable/Disable(CLIP PLANE{0-5})

–

n User-speciﬁed clipping planes are used predominately in engineering and scientiﬁc applications.

User clip planes can be emulated by calculating the dot product of the user clip plane with the vertex

position in eye space in the vertex shader. This term can be deﬁned as a varying variable. The

fragment shader can reject the pixel based on the value of this term. Depending on the ﬂoat pre-

cision types supported in a fragment shader, there may be clipping artifacts because of insufﬁcient

precision. q

2.13 Current Raster Position

The concept of the current raster position for positioning pixel rectangles and bitmaps is not supported.

Current raster state and commands for setting the raster position are not supported.

OpenGL 2.0

Common

RasterPos{2,3,4}{sifd}[v](T coords)

–

WindowPos{2,3}{sifd}[v](T coords)

–

n Bitmaps and pixel image primitives are not supported so there is no need to specify the raster

position. q

2.14 Colors and Coloring

The OpenGL 2.0 ﬁxed function lighting model is no longer supported.

OpenGL 2.0

Common

void FrontFace(enum mode)



void Enable/Disable(LIGHTING)

–

void Enable/Disable(LIGHT{0-7})

–

void Materialf[v](enum face, enum pname, T param)

–

void Materiali[v](enum face, enum pname, T param)

–

void GetMaterialfv(enum face, enum pname, T

params)

–

OpenGL Operation 11

OpenGL 2.0

Common

void GetMaterialiv(enum face, enum pname, T

params)

–

void Lightf[v](enum light, enum pname, T param)

–

void Lighti[v](enum light, enum pname, T param)

–

void GetLightfv(enum light, enum pname, T

params)

–

void GetLightiv(enum light, enum pname, T

params)

–

void LightModelf[v](enum pname, T param)

–

void LightModeli[v](enum pname, T param)

–

void Enable/Disable(COLOR MATERIAL)

–

void ColorMaterial(enum face, enum mode)

–

void ShadeModel(enum mode)

–

n The OpenGL 2.0 or any user deﬁned lighting can be implemented by writing appropriate vertex

and/or pixel shaders.

ShadeModel is no longer supported as ﬂat vs. gouraud shading only applied to the predeﬁned color

vertex attribute. Predeﬁned vertex attributes are not supported by OpenGL ES 2.0. q

2.15 Vertex Shaders

OpenGL 2.0 supports the ﬁxed function vertex pipeline and a programmable vertex pipeline using vertex

shaders. OpenGL ES 2.0 supports the programmable vertex pipeline only. OpenGL ES 2.0 allows applica-

tions to describe operations that occur on vertex values and their associated data by using a vertex shader.

OpenGL ES 2.0 provides interfaces to directly load pre-compiled shader binaries, or to load the shader

sources and compile them. An OpenGL ES implementation must support one of these methods for loading

shaders.

2.15.1 Loading and Compiling Shader Sources

The ShaderSource command loads source code into a vertex or a fragment shader object. Once the source

code for a shader has been loaded, a shader object can be compiled using the CompileShader command. A

string that contains information about the last compilation attempt on a shader object, called the info log,

can be obtained with the GetShaderInfoLog command. The GetShaderSource command returns the shader

source for the speciﬁed shader object.

The ReleaseShaderCompiler command allows the OpenGL ES implementation to release the resources

allocated by the shader compiler. This is a hint from the application and is no indicator that the compiler

will not be used in the future. If shader sources are loaded and compiled after ReleaseShaderCompiler has

been called, the CompileShader call is supposed to successfully compile the shaders provided there are no

errors in the shader source(s).

The GetShaderPrecisionFormat command returns the range and precision for various precision formats

supported by the implementation.

void GetShaderPrecisionFormat(enum shadertype, enum precisiontype, int *range, int *precision)

shadertype must be VERTEX SHADER or FRAGMENT SHADER. precisiontype can be LOW FLOAT, MEDIUM -

FLOAT, HIGH FLOAT, LOW INT, MEDIUM INT or HIGH INT. range returns the minimum and maximum

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