**Name**- gl.Ortho -- multiply the current matrix with an orthographic matrix
**Synopsis**-
gl.Ortho(left, right, bottom, top, zNear, zFar)

**Function**-
`gl.Ortho()`

describes a transformation that produces a parallel projection. The current matrix (See gl.MatrixMode for details.) is multiplied by this matrix and the result replaces the current matrix, as if gl.MultMatrix() were called with the following matrix as its argument:A 0 0 tx 0 B 0 ty 0 0 C tz 0 0 0 1

where

A = 2 / (right - left) B = 2 / (top - bottom) C = -2 / (far - near) tx = -(right + left) / (right - left) ty = -(top + bottom) / (top - bottom) tz = -(zFar + zNear) / (zFar - zNear)

Typically, the matrix mode is

`#GL_PROJECTION`

, and (left, bottom, -zNear) and (right, top, -zNear) specify the points on the near clipping plane that are mapped to the lower left and upper right corners of the window, respectively, assuming that the eye is located at (0, 0, 0). -zFar specifies the location of the far clipping plane. Both zNear and zFar can be either positive or negative.Use gl.PushMatrix() and gl.PopMatrix() to save and restore the current matrix stack.

Please consult an OpenGL reference manual for more information.

**Inputs**-
*left*- specify the coordinate for the left vertical clipping plane
*right*- specify the coordinate for the right vertical clipping plane
*bottom*- specify the coordinate for the bottom horizontal clipping plane
*top*- specify the coordinate for the top horizontal clipping plane
*zNear*- specify the distance to the nearer depth clipping plane; this value is negative if the plane is to be behind the viewer
*zFar*- specify the distance to the farther depth clipping plane; this value is negative if the plane is to be behind the viewer

**Errors**-
`#GL_INVALID_VALUE`

is generated if left = right, or bottom = top, or zNear = zFar.`#GL_INVALID_OPERATION`

is generated if`gl.Ortho()`

is executed between the execution of gl.Begin() and the corresponding execution of gl.End(). **Associated gets**-
gl.Get() with argument
`#GL_MATRIX_MODE`

gl.Get() with argument

`#GL_MODELVIEW_MATRIX`

gl.Get() with argument

`#GL_PROJECTION_MATRIX`

gl.Get() with argument

`#GL_TEXTURE_MATRIX`

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