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OpenGL OpenGL clipping at odd distances from the screen

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I'm learning modern OpenGL after dabbling with NeHes tutorials a few years ago. I started following the tutorials here, but I ended up with a problem when I got to the fifth tutorial in the "basics" arc. It required the C++ library GLM, which doesn't have a binding for D, which is the language I'm using for this. Having written up the code now for a simple set of matrix and vector routines, I'm testing and getting some weird results. First off, my rotating cube seems to be horrifically skewed and stretched, but only when I introduce my camera and frustum matrices. Secondly, my cube seems to start clipping when it reaches closer than 0.4 in Z screen space. I have confirmed both my matrix multiplication code, and my frustum matrix having the correct values. I'm not sure what it could be that is affecting this, so this is the code for my "idle" function which is called whenever the "update" function has returned;

auto cam = new camera;cam.translate( move_x, 0, move_z+2 );
auto model = new matrix;

// frustum matches glFrustum, see that function for arguments
auto frust = frustum(-0.5, 0.5, -0.5, 0.5, 0.1, 100 );
auto axis = (new vector( 1, 1, 1 )).normalize;
model.translate( move, 0, 0 );
model.rotate( angle, axis );
model.scale( 0.3 );

matrix transform = model * cam * frust;

glUseProgram( program );
if( trans_m != -1 )
  glUniformMatrix4fv( trans_m, 1, GL_FALSE, transform.cols.ptr );

While the drawing code just takes the vertices and colours and renders them, and the shader uses the matrix created above to transform each vertex. The cube stretches off into the distance, clips before reaching the camera, and skews when viewed from even slightly a different angle to head-on. Needless to say, I'm getting frustrated. I know there probably isn't enough here to go on, but to avoid an info-dump, if you could let me know which parts you would like to look at to work this out, I'll post them up ASAP.

Thanks in advance for any help.

EDIT: OK, so plenty of views, but no answers? Is it just that people don't have enough experience in D to help, or would it help if I add some more code? I'll include my math module below, sans any functions not being used at the moment, if that helps:

module math3d;

/+

OpenGL GLSL matrices;

Matrices are in column order, so:
    [ 0, 4,  8, 12 ]
    [ 1, 5,  9, 13 ]
    [ 2, 6, 10, 14 ]
    [ 3, 7, 11, 15 ]

Translation matrix is:
    [ 1, 0, 0, x ]
    [ 0, 1, 0, y ]
    [ 0, 0, 1, z ]
    [ 0, 0, 0, 1 ]

Rotation( angle, axis ) matrix is:
    [ (x^2)*(1-cos(angle))+cos(angle), x*y*(1-cos(angle))-z*sin(angle), x*z*(1-cos(angle))+y*sin(angle), 0 ]
    [ x*y*(1-cos(angle))+z*sin(angle), (y^2)*(1-cos(angle))+cos(angle), y*z*(1-cos(angle))-x*sin(angle), 0 ]
    [ x*z*(1-cos(angle))-y*sin(angle), y*z*(1-cos(angle))+x*sin(angle), (z^2)*(1-cos(angle))+cos(angle), 0 ]
    [                 0,                                    0,                                0,                 1 ]

Scale matrix is:
    [ x, 0, 0, 0 ]
    [ 0, y, 0, 0 ]
    [ 0, 0, z, 0 ]
    [ 0, 0, 0, 1 ]

+/

public import std.math;

import std.stdio;

class vector{
    float[4] array;
    
    this( float a, float b, float c, float d = 1.0f ){
        array = [ a, b, c, d ];
    }
    
    this(){
        this( 0.0, 0.0, 0.0 );
    }
    
    this( float[4] r ){
        array = r;
    }
    
    this( float[] r ){
        if( r.length >=4 )
            array = r;
        else{
            array[0..r.length] = r;
            array[r.length..$] = 0;
            array[3] = 1;
        }
    }
    
    @property float x(){ return array[0]; }
    @property float y(){ return array[1]; }
    @property float z(){ return array[2]; }
    @property float w(){ return array[3]; }
    
    @property float x( float c ){ return array[0] = c; }
    @property float y( float c ){ return array[1] = c; }
    @property float z( float c ){ return array[2] = c; }
    @property float w( float c ){ return array[3] = c; }
    
    vector opBinary( string op )( vector v ){
        return mixin( "new vector( array"~op~"v.array )" );
    }
    
    vector opBinary( string op )( matrix m ){
        vector ret = new vector;
        static if( op == "*" ){
            ret.x = x*m.cols[0][0] + x*m.cols[0][1] + x*m.cols[0][2] + x*m.cols[0][3];
            ret.y = y*m.cols[0][0] + y*m.cols[0][1] + y*m.cols[0][2] + y*m.cols[0][3];
            ret.z = z*m.cols[0][0] + z*m.cols[0][1] + z*m.cols[0][2] + z*m.cols[0][3];
            ret.w = w*m.cols[0][0] + w*m.cols[0][1] + w*m.cols[0][2] + w*m.cols[0][3];
        }
    }
    
    vector normalize(){
        import std.math;
        
        auto sqr = (x*x)+(y*y)+(z*z);
        if( sqr != 1.0f ){
            auto srt = sqrt( sqr );
            array[0] /= srt;
            array[1] /= srt;
            array[2] /= srt;
            array[3]  = 1;
        }
        
        return this;
    }
}

/// simple matrix class. Matrix values are stored in the array in OpenGL( i.e.; column-major ) order.
class matrix{
    float[16] cols;
    private matrix previous;
    
    /// allows us to treat the matrix as though it were the array of 16 floats
    alias cols this;
    
    ////////////////
    // CONSTRUCTORS
    ////////////////
    this(){
        cols =
            [ 1.0, 0.0, 0.0, 0.0,
              0.0, 1.0, 0.0, 0.0,
              0.0, 0.0, 1.0, 0.0,
              0.0, 0.0, 0.0, 1.0 ];
        
    }
    
    this( float[16] vals ){
        cols = vals.dup;
    }
    
    this( float[4][4] vals ){
        cols = vals[0]~vals[1]~vals[2]~vals[3];
    }
    
    this( matrix m ){
        cols = m.cols.dup;
    }
    
    /// returns an identity matrix.
    /// Not difficult, as the identity matrix is the default for the matrix class
    static matrix identity(){
        return new matrix();
    }
    
    /// operator overloading. Currently only overloads the '*' operator.
    matrix opBinary( string op )( matrix m ){
        matrix r = new matrix;
        
        /++
        
        At the moment, if the matrices are layed out in the following way;
        
                               [ t00 t04 t08 t12 ]
                               [ t01 t05 t09 t13 ]
                               [ t02 t06 t10 t14 ]
                               [ t03 t07 t11 t15 ]
        
        [ m00 m04 m08 m12 ]    [ r00 r04 r08 r12 ]
        [ m01 m05 m09 m13 ]    [ r01 r05 r09 r13 ]
        [ m02 m06 m10 m14 ]    [ r02 r06 r10 r14 ]
        [ m03 m07 m11 m15 ]    [ r03 r07 r11 r15 ]
        
        where rXX is the resulting value, tXX is the "this" matrix, and mXX is
        the passed-in matrix. If the matrices are messing up, then I may need to
        switch the m and t matrices.
        
        ++/
        static if( op == "*" ){
            auto t = cols;
            r[0]  = m[0]*t[0]  + m[4]*t[1]  + m[8]* t[2]  + m[12]*t[3];
            r[1]  = m[1]*t[0]  + m[5]*t[1]  + m[9]* t[2]  + m[13]*t[3];
            r[2]  = m[2]*t[0]  + m[6]*t[1]  + m[10]*t[2]  + m[14]*t[3];
            r[3]  = m[3]*t[0]  + m[7]*t[1]  + m[11]*t[2]  + m[15]*t[3];
            
            r[4]  = m[0]*t[4]  + m[4]*t[5]  + m[8]* t[6]  + m[12]*t[7];
            r[5]  = m[1]*t[4]  + m[5]*t[5]  + m[9]* t[6]  + m[13]*t[7];
            r[6]  = m[2]*t[4]  + m[6]*t[5]  + m[10]*t[6]  + m[14]*t[7];
            r[7]  = m[3]*t[4]  + m[7]*t[5]  + m[11]*t[6]  + m[15]*t[7];
            
            r[8]  = m[0]*t[8]  + m[4]*t[9]  + m[8]* t[10] + m[12]*t[11];
            r[9]  = m[1]*t[8]  + m[5]*t[9]  + m[9]* t[10] + m[13]*t[11];
            r[10] = m[2]*t[8]  + m[6]*t[9]  + m[10]*t[10] + m[14]*t[11];
            r[11] = m[3]*t[8]  + m[7]*t[9]  + m[11]*t[10] + m[15]*t[11];
            
            r[12] = m[0]*t[12] + m[4]*t[13] + m[8]* t[14] + m[12]*t[15];
            r[13] = m[1]*t[12] + m[5]*t[13] + m[9]* t[14] + m[13]*t[15];
            r[14] = m[2]*t[12] + m[6]*t[13] + m[10]*t[14] + m[14]*t[15];
            r[15] = m[3]*t[12] + m[7]*t[13] + m[11]*t[14] + m[15]*t[15];
            
        }
        else static assert( 0, "Unsupported binary op in math3d.matrix: "~op );
        
        return r;
    }
    
    /// utility method to perform a translation on a matrix
    matrix translate( vector v ){
        return translate( v.x, v.y, v.z );
    }
    
    /// utility method to perform a translation on a matrix
    matrix translate( float x, float y, float z ){
        
        cols[0] += cols[3]*x;    cols[4] += cols[7]*x;    cols[8] += cols[11]*x;    cols[12] += cols[15]*x;
        cols[1] += cols[3]*y;    cols[5] += cols[7]*y;    cols[9] += cols[11]*y;    cols[13] += cols[15]*y;
        cols[2] += cols[3]*z;    cols[6] += cols[7]*z;    cols[10] += cols[11]*z;    cols[14] += cols[15]*z;
        
        version(test_matrix) print(this);
        return this;
    }
    
    /// utility method to perform a rotation on a matrix
    matrix rotate( float angle, vector axis ){
        version(test_matrix) writefln("entered rotate(float, vector(%s))", axis);
        return rotate( angle, axis.x, axis.y, axis.z );
        version(test_matrix) writeln("leaving rotate(float, vector)");
    }
    
    /// utility method to perform a rotation on a matrix
    matrix rotate( float angle, float x, float y, float z ){
        version(test_matrix) writefln( "entered rotate(%s, %s, %s, %s)", angle, x, y, z );
        matrix m = new matrix;
        version(test_matrix) writeln( "\nmatrix m before construction of rotation" );
        
        float c = cos(angle*(PI/180.0));
        float s = sin(angle*(PI/180.0));
        version(test_matrix){
            writefln( "c: %s\ns: %s\n", c, s );
            writefln( "cos(angle*(PI/180.0)): %s\nsin(angle*(PI/180.0)): %s\n", cos(angle*(PI/180.0)), sin(angle*(PI/180.0)) );
        }
        
        auto xx = x*x,            xy = x*y,
             xz = x*z,            yy = y*y,
             yz = y*z,            zz = z*z;
        
        m.cols[0] = xx * (1 - c) + c;
        m.cols[1] = xy * (1 - c) + z * s;
        m.cols[2] = xz * (1 - c) - y * s;
        m.cols[3]= 0;
        m.cols[4] = xy * (1 - c) - z * s;
        m.cols[5] = yy * (1 - c) + c;
        m.cols[6] = yz * (1 - c) + x * s;
        m.cols[7]= 0;
        m.cols[8] = xz * (1 - c) + y * s;
        m.cols[9] = yz * (1 - c) - x * s;
        m.cols[10]= zz * (1 - c) + c;
        m.cols[11]= 0;
        m.cols[12] = 0;
        m.cols[13] = 0;
        m.cols[14]= 0;
        m.cols[15]= 1;
        
        version(test_matrix){
            writeln( "\nmatrix m after rotation created:" );
            print(m);
        }
        
        cols = ( m*this ).cols;
        
        version(test_matrix){
            writeln( "\nfinal matrix after rotation applied:" );
            print(this);
        }
        
        version(test_matrix) writeln("leaving rotate(float, float, float, float)");
        return this;
    }
    
    matrix rotateX( float angle ){
        version(test_matrix) writeln("entered rotateX");
        return rotate( angle, 1.0, 0.0, 0.0 );
    }
    matrix rotateY( float angle ){
        version(test_matrix) writeln("entered rotateY");
        return rotate( angle, 0.0, 1.0, 0.0 );
    }
    matrix rotateZ( float angle ){
        version(test_matrix) writeln("entered rotateX");
        return rotate( angle, 0.0, 0.0, 1.0 );
    }
    
    /// utility method to scale the matrix
    matrix scale( vector v ){
        return scale( v.x, v.y, v.z );
    }
    
    matrix scale( float f ){
        return scale( f, f, f );
    }
    
    matrix scale( float x, float y, float z ){
        cols[0] = cols[0]*x;   cols[1] = cols[1]*x;   cols[2] = cols[2]*x;   cols[3] = cols[3]*x;
        cols[4] = cols[4]*y;   cols[5] = cols[5]*y;   cols[6] = cols[6]*y;   cols[7] = cols[7]*y;
        cols[8] = cols[8]*z;   cols[9] = cols[9]*z;   cols[10]= cols[10]*z;  cols[11]= cols[11]*z;
        
        return this;
    }
}

/// replacement for gluPerspective. Matches the parameters and results as accurately as the floats allow
matrix perspective( float fovInDeg, float aspectRatio, float znear, float zfar ){
    float ymax, xmax;
    ymax = znear * tan( fovInDeg * PI / 360.0 );
    xmax = ymax * aspectRatio;
    return frustum( -xmax, xmax, -ymax, ymax, znear, zfar );
}

/// replacement for glFrustum. Matches the parameters and results as accurately as the floats allow
matrix frustum( float left, float right, float bottom, float top, float znear, float zfar ){
    float t1, t2, t3, t4;
    t1 = 2.0 * znear;
    t2 = right - left;
    t3 = top - bottom;
    t4 = zfar - znear;
    
    return new matrix(
        [
            t1/t2, 0, 0, 0,
            0, t1/t3, 0, 0,
            (right + left)/t2, (top + bottom)/t3, -(zfar + znear)/t4, -1,
            0, 0, -(t1*zfar)/t4, 0
        ]
    );
}

I hope this helps, and I'd appreciate any help you guys can give me

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      #version 450 core layout(location=0) in vec3 inPos; layout(location=1) in vec2 inTexCoord; out vec2 TexCoord; void main() { gl_Position=vec4(inPos,1.0); TexCoord=inTexCoord; } and the fragment shader
      #version 450 core in vec2 TexCoord; uniform sampler2D inTextureOne; uniform sampler2D inTextureTwo; out vec4 FragmentColor; void main() { FragmentColor=mix(texture(inTextureOne,TexCoord),texture(inTextureTwo,TexCoord),0.2); } I was expecting awesomeface.png on top of container.jpg

    • By khawk
      We've just released all of the source code for the NeHe OpenGL lessons on our Github page at https://github.com/gamedev-net/nehe-opengl. code - 43 total platforms, configurations, and languages are included.
      Now operated by GameDev.net, NeHe is located at http://nehe.gamedev.net where it has been a valuable resource for developers wanting to learn OpenGL and graphics programming.

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    • By TheChubu
      The Khronos™ Group, an open consortium of leading hardware and software companies, announces from the SIGGRAPH 2017 Conference the immediate public availability of the OpenGL® 4.6 specification. OpenGL 4.6 integrates the functionality of numerous ARB and EXT extensions created by Khronos members AMD, Intel, and NVIDIA into core, including the capability to ingest SPIR-V™ shaders.
      SPIR-V is a Khronos-defined standard intermediate language for parallel compute and graphics, which enables content creators to simplify their shader authoring and management pipelines while providing significant source shading language flexibility. OpenGL 4.6 adds support for ingesting SPIR-V shaders to the core specification, guaranteeing that SPIR-V shaders will be widely supported by OpenGL implementations.
      OpenGL 4.6 adds the functionality of these ARB extensions to OpenGL’s core specification:
      GL_ARB_gl_spirv and GL_ARB_spirv_extensions to standardize SPIR-V support for OpenGL GL_ARB_indirect_parameters and GL_ARB_shader_draw_parameters for reducing the CPU overhead associated with rendering batches of geometry GL_ARB_pipeline_statistics_query and GL_ARB_transform_feedback_overflow_querystandardize OpenGL support for features available in Direct3D GL_ARB_texture_filter_anisotropic (based on GL_EXT_texture_filter_anisotropic) brings previously IP encumbered functionality into OpenGL to improve the visual quality of textured scenes GL_ARB_polygon_offset_clamp (based on GL_EXT_polygon_offset_clamp) suppresses a common visual artifact known as a “light leak” associated with rendering shadows GL_ARB_shader_atomic_counter_ops and GL_ARB_shader_group_vote add shader intrinsics supported by all desktop vendors to improve functionality and performance GL_KHR_no_error reduces driver overhead by allowing the application to indicate that it expects error-free operation so errors need not be generated In addition to the above features being added to OpenGL 4.6, the following are being released as extensions:
      GL_KHR_parallel_shader_compile allows applications to launch multiple shader compile threads to improve shader compile throughput WGL_ARB_create_context_no_error and GXL_ARB_create_context_no_error allow no error contexts to be created with WGL or GLX that support the GL_KHR_no_error extension “I’m proud to announce OpenGL 4.6 as the most feature-rich version of OpenGL yet. We've brought together the most popular, widely-supported extensions into a new core specification to give OpenGL developers and end users an improved baseline feature set. This includes resolving previous intellectual property roadblocks to bringing anisotropic texture filtering and polygon offset clamping into the core specification to enable widespread implementation and usage,” said Piers Daniell, chair of the OpenGL Working Group at Khronos. “The OpenGL working group will continue to respond to market needs and work with GPU vendors to ensure OpenGL remains a viable and evolving graphics API for all its customers and users across many vital industries.“
      The OpenGL 4.6 specification can be found at https://khronos.org/registry/OpenGL/index_gl.php. The GLSL to SPIR-V compiler glslang has been updated with GLSL 4.60 support, and can be found at https://github.com/KhronosGroup/glslang.
      Sophisticated graphics applications will also benefit from a set of newly released extensions for both OpenGL and OpenGL ES to enable interoperability with Vulkan and Direct3D. These extensions are named:
      GL_EXT_memory_object GL_EXT_memory_object_fd GL_EXT_memory_object_win32 GL_EXT_semaphore GL_EXT_semaphore_fd GL_EXT_semaphore_win32 GL_EXT_win32_keyed_mutex They can be found at: https://khronos.org/registry/OpenGL/index_gl.php
      Industry Support for OpenGL 4.6
      “With OpenGL 4.6 our customers have an improved set of core features available on our full range of OpenGL 4.x capable GPUs. These features provide improved rendering quality, performance and functionality. As the graphics industry’s most popular API, we fully support OpenGL and will continue to work closely with the Khronos Group on the development of new OpenGL specifications and extensions for our customers. NVIDIA has released beta OpenGL 4.6 drivers today at https://developer.nvidia.com/opengl-driver so developers can use these new features right away,” said Bob Pette, vice president, Professional Graphics at NVIDIA.
      "OpenGL 4.6 will be the first OpenGL release where conformant open source implementations based on the Mesa project will be deliverable in a reasonable timeframe after release. The open sourcing of the OpenGL conformance test suite and ongoing work between Khronos and X.org will also allow for non-vendor led open source implementations to achieve conformance in the near future," said David Airlie, senior principal engineer at Red Hat, and developer on Mesa/X.org projects.

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    • By _OskaR
      Hi,
      I have an OpenGL application but without possibility to wite own shaders.
      I need to perform small VS modification - is possible to do it in an alternative way? Do we have apps or driver modifictions which will catch the shader sent to GPU and override it?
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