Shaders Error Invalid Program Deferred

[Lawana Stuckert]

Ahthe files were not in the dir of the arena.py I moved them and the program started but it was mostly black. I was just able to see the gun in the hand and it constantly printed (in the terminal of vs-code) this:

:display:gsg:glgsg(error): GL error 0x506 : invalid framebuffer operation

:display:gsg:glgsg(error): An OpenGL error has occurred. Set gl-debug #t in your PRC file to display more information.

? A step-by-step guide to implementing SSAO, depth of field, lighting, normal mapping, and more for your 3D game. - GitHub - lettier/3d-game-shaders-for-beginners: ? A step-by-step guide to impleme...

Shader Compilation is the term used to describe the process by which OpenGL Shading Language scripts are loaded into OpenGL to be used as shaders. OpenGL has three ways to compile shader text into usable OpenGL objects. All of these forms of compilation produce a Program Object.

A Program Object can contain the executable code for all of the Shader stages, such that all that is needed to render is to bind one program object. Building programs that contain multiple shader stages requires a two-stage compilation process.

This two-stage compilation process mirrors the standard compile/link setup for C and C++ source code. C/C++ text is first fed through a compiler, thus producing an object file. To get the executable code, one or more object files must be linked together.

With this method of program creation, shader text is first fed through a compiler, thus producing a shader object. To get the executable program object, one or more shader objects must be linked together.

When the shader is compiled, it will be compiled as if all of the given strings were concatenated end-to-end. This makes it easy for the user to load most of a shader from a file, but to have a standardized preamble that is prepended to some group of shaders.

Shader compilation is pass/fail, but it is often useful to know why. This, like in most languages, is provided as text messages. OpenGL allows you to query a log containing this information. First, you must use glGetShaderiv to query the log's length:

If one of these is defined in one stage, another stage can define the same object with the same name and the exact same definition. If this happens, then there will only be one uniform/buffer variable/interface block visible from the introspection API. So shader stages in the same program can share uniform variables, allowing the same value to be set into both stages with one glUniform call.

For this to work however, the definitions must be exactly the same. This includes the order of the members, any user-defined data structures they use, array counts, everything. If two definitions in different stages have the same name, but different definitions, then there will be a linker error.

If you do not intend to use this particular shader object in the linking of another program, you may delete it. This is done via glDeleteShader. Note that the deletion of a shader is deferred until the shader object is no longer attached to a program. Therefore, it is a good idea to detach shaders after linking.

A program object can contain the code for multiple shader stages. The glUseProgram function only takes a single program, so you can only use a single program at a time for rendering. Therefore, you cannot mix-and-match code for different shader stages dynamically post-linking. Shader objects are not programs; they only hold compiled fragments of code, not fully useful programs.

To allow the use of multiple programs, where each program only provides some of the shader stage code, we must first create our programs specially. To signal that a program object is intended to be used with this separate program model, we must set a parameter on the program before linking. This is done as follows:

There is an alternative method for creating separable programs. This represents a common use case: creating a program from a single set of shader source which provides the code for a single shader stage. The function to do this is:

Separable programs are allowed to have shaders from more than one stage linked into them. While it is best to only use shaders from one stage (since the main point of using separable programs is the ability to mix-and-match freely), you do not have to. However, if two stages are linked together in the same program, you will be unable to insert another program between those two stages, due to pipeline validation rules.

To use multiple separable programs, they must first be assembled into an OpenGL Object type called a program pipeline. Unlike program or shader objects, these follow the standard OpenGL Object mode. Therefore, there is a glGenProgramPipelines function to create new pipeline names, a glDeleteProgramPipelines to delete them, and a glBindProgramPipeline to bind it to the context. Program pipeline objects do not have targets, so the last function only takes the pipeline to be bound.

Similar to Sampler Objects, program pipeline objects should only be bound when you intend to render with them (or set uniforms through them, as described below). The only state in program pipeline objects are the list of programs that contain the code for the various shader stages. This state is set by this function:

Once you have a functioning program pipeline with all of the separate stages you would like to use, you can render with it. To do that, you must first bind the program pipeline with glBindProgramPipeline.

glUniform changes uniform state on the currently used program. However, with separate programs and program pipelines, the definition of "currently used program" is much more complicated. It works as follows.

OpenGL first checks the program currently set by glUseProgram (you can bind separable programs with this function). If a program is bound through this function, then that is the currently used program. If no program is set by this function (ie: if you execute glUseProgram(0)), then the next step occurs.

The currently bound program pipeline is checked. Program pipelines have the concept of an active program. The active program of a program pipeline object is the "currently used program" (again, only if a program isn't in use by glUseProgram).

The following examples depict multiple possible scenarios when using separable programs. The first example aims at showing the simplicity inherent in using glCreateShaderProgramv. The second shows how to deal with multi-stage programs and doing some pre-linking work not possible when creating single-stage, separable programs.

Compiling and linking shaders, regardless of which method you use, can take a long time. The more shaders you have, the longer this process takes. It is often useful to be able to cache the result of program linking, so that this cached program can be reloaded much faster.

This is done via a set of calls. Given a successfully linked program, the user can fetch a block of binary data, in a certain format, that represents this program. The first step of this process is to get the length of this data by calling glGetProgram with GL_PROGRAM_BINARY_LENGTH on the program. Armed with this length, the actual binary can be obtained with this function:

Program objects contain certain state. The program binary only encapsulates the state of the program at the moment linking was successful. This means that all uniforms are reset to their default values (either specified in-shader or 0). Vertex attributes and fragment shader outputs will have the values assigned, as well as transform feedback data, interface block bindings, and so forth.

Program binary formats are not intended to be transmitted. It is not reasonable to expect different hardware vendors to accept the same binary formats. It is not reasonable to expect different hardware from the same vendor to accept the same binary formats.

Indeed, you cannot expect the cached version to work even on the same machine. Driver updates between when the data was cached and when it is reloaded can change the acceptable binary formats. Therefore, glProgramBinary can fail frequently. If you use this functionality, you must have a fallback for creating your shaders if the binary is rejected.

The use of this function will replace the shaders specified by previous calls to glShaderSource or glShaderBinary. Loading a non-SPIR-V binary or loading GLSL source strings into the program will make it no longer contain SPIR-V code.

Before a SPIR-V shader object can be used, you must specify which entry-point to use and provide values for any specialization constants used by that entry-point. This is done through a single function:

Specializing a SPIR-V shader is analogous to compiling a GLSL shader. So if this function completes successfully, the shader object's compile status is GL_TRUE. If specialization fails, then the shader infolog has information explaining why and an OpenGL Error is generated.

SPIR-V shader objects that have been specialized can be used to link programs (separable or otherwise). If you link multiple shader objects in the same program, then either all of them must be SPIR-V shaders or none of them may be SPIR-V shaders. You cannot link SPIR-V to non-SPIR-V shaders in a program.

Program linking is pass/fail, but it is often useful to know why it failed. Like in most languages, linker errors are provided as text messages. OpenGL allows you to query a log containing these errors. To do so, you must first query the log's length using glGetProgramiv again:

When linking multiple shader stages together, these rules are checked at program linking time. Therefore, mismatching interfaces between stages are linker errors. However, the interface between separable programs in a pipeline can only be checked at runtime, when the pipeline is used.

Directly linking multiple shader stages together requires that all outputs from one stage are consumed by inputs from the next active stage and vice versa. Failure to do this results in a linker error. However, separable programs do not have exactly match between the separate programs. The results of an inexact match are described below.

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