Class TGLSLProgram

Create shader from given string, compile it and attach to current program.

For desktop OpenGL, you can attach more than one shader of given type, just make sure that only one main() function is among each type (otherwise link error will be raised later). For OpenGLES, this is not allowed, so don't use this if you want to work with OpenGLES too.

If you want to explicitly get rid of old shaders, use DetachAllShaders.

Exceptions raised

EGLSLShaderCompileError

If the shader source code cannot be compiled, exception message contains precise description from OpenGL where the error is.

Attach multiple shader parts for given type.

For normal OpenGL, we can use GLSL separate compilation units. So this is equivalent to just calling AttachShader(ShaderType, Parts[I]) for each part.

For OpenGL ES, this is unfortunately not possible, you can only attach a single shader of a given type (see http://www.khronos.org/opengles/sdk/docs/man/xhtml/glAttachShader.xml ). So we simply concatenate the shaders into one.

Specify values to record in transform feedback buffers. This must be called before Link method.

Link the program, this should be done after attaching all shaders and before actually using the program.

Exceptions raised

EGLSLProgramLinkError

If the program cannot be linked, exception message contains precise description from OpenGL where the error is.

Warning: this symbol is deprecated: use parameterless Link method

Enable (use) this program. Shortcut for RenderContext.CurrentProgram := Self.

Disable this program (use the fixed function pipeline). Shortcut for RenderContext.CurrentProgram := nil.

Override this to set uniform values, in particular to bind the textures used by this shader, right after each Enable call.

This is automatically called after every Enable by our renderer (when it renders shapes) or TCastleScreenEffect (when it renders screen effects). If you use this TGLSLProgram directly (if you call Enable yourself), then it's your responsibility to call this method explicitly, if you want shaders using it to work.

You can set any uniform values, and generally do anything you want to be done each time this shader is enabled. In particular, you can bind textures and set corresponding uniform variables of them. Increase BoundTextureUnits appropriately.

Returns False is some texture couldn't be bound.

Returns multiline debug info about current program. Things like how it's supported (not at all ? ARB extension ? standard ?), names of active uniform and attribute variables etc.

fglrx (Radeon closed-source OpenGL drivers) are buggy (that's not news, I know...) and they report GL_INVALID_ENUM on some queries here. We detect this, and still produce nice debug message, without raising any exception (after all, we have to workaround fglrx bugs, and try to run our program anyway...). What's important for caller is that we have to check first whether there are any OpenGL errors pending, and raise exceptions on them.

Exceptions raised

EOpenGLError

If any OpenGL error will be detected.

This is program info log, given to you from OpenGL after the program is linked.

After the program is linked, you can check this.

Note that this is necessarily implemented in quite hacky way (by looking at ProgramInfoLog), there is no way currently (AFAIK ?) to get this information cleanly from OpenGL. In case of doubts, we try to "trust" OpenGL to execute shader in hardware. Return False only when we see clear indication in ProgramInfoLog that it'll run in software.

Warning: this symbol is deprecated: use GLFeatures.Shaders

What support do we get from current OpenGL context ?

This is much like Support, but it's a class function.

Get the uniform instance. It can be used to make repeated TGLSLUniform.SetValue calls. You must link the program first.

If the uniform doesn't exist (or is unused), the action we take depends on UniformMissing property (by default – umWarning). The overloaded version with extra AUniformMissing parameter follows this parameter value.

Set appropriate uniform variable value. The used type must match the type of this variable in GLSL program.

OpenGL forces some constraints on using this:

• This should be used only after linking, and re-linking clears (sets to zero) all uniform variables values.

• This GLSL program must be currently enabled for this to work. So calling this automatically calls Enable and sets RenderContext.CurrentProgram.

  This is required by OpenGL glUniform* commands. glGetUniformLocation take program id as parameter, so they can operate on any program. But glUniform* operate only on active program.

• Only active uniforms variables may be set. Active means, quoting OpenGL manpages, a variable that is determined during the link operation that it may be accessed during program execution. In other words, when linking GLSL program, unused variables may be eliminated, and you cannot set them by SetUniform.

  Call DebugInfo to see what uniform variables are considered active for your shader.

  You can change UniformMissing not to silently ignore setting of inactive (or not existing) uniform values.

This will make warning if the variable is not found within the program and UniformMissing = umWarning. The overloaded version with explicit AUniformMissing parameter uses that to decide whether to show warning.

Get the attribute instance. It can be used to make repeated TGLSLAttribute.SetValue and TGLSLAttribute.EnableArray.

Exceptions raised

EGLSLAttributeNotFound

If the variable is not found within the program.

Note that this is only one of the many things that can go wrong. And on most cases we don't raise any error, instead OpenGL sets it's error state and you probably want to call CheckGLErrors from time to time to catch them.

Get the attribute instance. It can be used to make repeated TGLSLAttribute.SetValue and TGLSLAttribute.EnableArray.

Returned attribute has TGLSLAttribute.Location equal to -1. All the calls to TGLSLAttribute.SetValue or TGLSLAttribute.EnableArray or TGLSLAttribute.DisableArray methods are silently ignored.

Warning: this symbol is deprecated: use TGLSLAttribute.EnableArray

Load and enable vertex attribute data. This calls glVertexAttribPointer and enables it by glEnableVertexAttribArray (or ARB extension equivalents), see OpenGL reference for details.

The attribute name is automatically resolved to a "location". We add LocationOffset (useful if you want to load matrix attributes, when you have to load matrix columns separately, with LocationOffset = column index).

For repeated usage, it's better to use Attribute method, and repeatedly call TGLSLAttribute.EnableArray on the same TGLSLAttribute instance.

Returns

Attribute location (with LocationOffset already applied). You can use it with DisableVertexAttribArray.

Exceptions raised

EGLSLAttributeNotFound

If the variable is not found within the program.

Warning: this symbol is deprecated: use TGLSLAttribute.DisableArray

Warning: this symbol is deprecated: use TGLSLAttribute.SetValue

Set attribute variable value. The used type must match the type of this variable in GLSL program.

OpenGL forces some constraints on using this, see SetUniform. In short: use this only after linking the program. The program is automatically enabled (set as RenderContext.CurrentProgram) by this. And note that attributes declared but not actually used in shader code may be eliminated, use DebugInfo to see which attributes are actually used (active in OpenGL terminology).

These should not be often used. Usually, you should rather load attribute arrays, by VertexAttribPointer. You should also get attribute by the Attribute method, as TGLSLAttribute, and then call TGLSLAttribute.SetValue or TGLSLAttribute.EnableArray.

Exceptions raised

EGLSLAttributeNotFound

If the variable is not found within the program.

Note that this is only one of the many things that can go wrong. And on most cases we don't raise any error, instead OpenGL sets it's error state and you probably want to call CheckGLErrors from time to time to catch them.

Warning: this symbol is deprecated: use TGLSLAttribute.SetValue

Warning: this symbol is deprecated: use TGLSLAttribute.SetValue

Warning: this symbol is deprecated: use TGLSLAttribute.SetValue

Warning: this symbol is deprecated: use TGLSLAttribute.SetValue

Warning: this symbol is deprecated: use TGLSLAttribute.SetValue

Warning: this symbol is deprecated: use TGLSLAttribute.SetValue

Warning: this symbol is deprecated: use TGLSLAttribute.SetValue

Warning: this symbol is deprecated: use TGLSLAttribute.SetValue

Warning: this symbol is deprecated: use GLFeatures.Shaders

What to do when GLSL uniform variable is accessed (by SetUniform or Uniform) but doesn't exist in the shader. Note that OpenGL aggresively removes unused code and variables from the shader when compiling/linking, so this also happens for "declared but unused" variables.

This is only the default value, each Uniform method call may explicitly use other TUniformMissing.

See also

TUniformMissing

What to do when shader uniform variable is set but doesn't exist in the shader.

Warning: this symbol is deprecated: use RenderContext.CurrentProgram

Currently enabled GLSL program. Nil if fixed-function pipeline should be used. Setting this property encapsulates the OpenGL glUseProgram (or equivalent ARB extension), additionally preventing redundant glUseProgram calls.