hwUnlitShader/MTexture.h

#ifndef MAYA_API_MTexture
#define MAYA_API_MTexture

//-
// Copyright 2015 Autodesk, Inc. All rights reserved.
// 
// Use of this software is subject to the terms of the Autodesk
// license agreement provided at the time of installation or download,
// or which otherwise accompanies this software in either electronic
// or hard copy form.
//+

// MTexture.h

// DESCRIPTION: Texture object, that can be mipmapped. Eventually, this
//              class will likely end up in the Maya API.
//
// AUTHOR: Christian Laforte
//

#include <maya/MImage.h>
#include <maya/MString.h>
#include <assert.h>

#include <maya/MGL.h>

int highestPowerOf2(int num);

class TexObj
{
public:
    TexObj(GLenum target = GL_TEXTURE_2D)
    {
        assert(glGetError() == GL_NO_ERROR);

        // Get a texture identifier.
        glGenTextures(1, &fTextureNum);
        assert(glGetError() == GL_NO_ERROR);

        fTarget = target;

        // Set up default values for the texture parameters.
        // They are the same as the OpenGL default.
        fMinFilterParam = GL_NEAREST;
        fMagFilterParam = GL_LINEAR;
        fWrapSParam = GL_REPEAT;
        fWrapTParam = GL_REPEAT;
    }

    ~TexObj()
    {
        glDeleteTextures(1, &fTextureNum);
    }

    void bind()
    {
        assert(glGetError() == GL_NO_ERROR);

        // Bind the texture.
        glBindTexture(fTarget, fTextureNum);
        assert(glGetError() == GL_NO_ERROR);

        // Set up the texture parameters.
        glTexParameteri(fTarget, GL_TEXTURE_MIN_FILTER, fMinFilterParam);
        assert(glGetError() == GL_NO_ERROR);
        glTexParameteri(fTarget, GL_TEXTURE_MAG_FILTER, fMagFilterParam);
        assert(glGetError() == GL_NO_ERROR);
        glTexParameteri(fTarget, GL_TEXTURE_WRAP_S, fWrapSParam);
        assert(glGetError() == GL_NO_ERROR);
        glTexParameteri(fTarget, GL_TEXTURE_WRAP_T, fWrapTParam);
        assert(glGetError() == GL_NO_ERROR);
    }

    void parameter(GLenum pname, GLint param)
    {
        switch (pname)
        {
        case GL_TEXTURE_MIN_FILTER: fMinFilterParam = param;    break;
        case GL_TEXTURE_MAG_FILTER: fMagFilterParam = param;    break;
        case GL_TEXTURE_WRAP_S:     fWrapSParam = param;        break;
        case GL_TEXTURE_WRAP_T:     fWrapTParam = param;        break;
        }
    }

private:
    GLenum fTarget;

    // Various parameters. See glTexParameterf() in MSDN for more info.
    GLint fMinFilterParam;
    GLint fMagFilterParam;
    GLint fWrapSParam;
    GLint fWrapTParam;
    
    GLuint fTextureNum;
};

class MTexture
{
public:
    enum Type
    {
        RGBA,
        HILO,
        NMAP
    };

    MTexture();

    ~MTexture()
    {
        if (m_levels)
        {
            for (unsigned int i=0; i < m_numLevels; i++)
            {
                if (m_levels[i])
                {
                    delete [] m_levels[i];
                    m_levels[i] = NULL;
                }
            }
            
            delete [] m_levels;
        }
    }

    bool set(MImage &image, Type type, bool mipmapped = true, GLenum target = GL_TEXTURE_2D);

    // This function assumes that the file texture is square, and
    // that its dimensions are exponents of 2.
    bool load(MString filename, Type type, bool mipmapped = true, GLenum target = GL_TEXTURE_2D);
    
    bool specify(GLenum target);

    // Returns 1 if no mipmapping, >1 otherwise.
    unsigned int levels() { return m_numLevels; }

    bool bind();

    unsigned char* fetch(unsigned int s, unsigned int t, unsigned int level = 0)
    {
        // Verify that the mipmap level exists.
        if (level > m_numLevels || m_levels == NULL || m_levels[level] == NULL)
            return NULL;
        
        return internalFetch(s, t, level);
    }
    
    inline bool square()
    {
        return m_width == m_height;
    }

    inline bool mipmapped()
    {
        return levels() > 1;
    }

    // Return the width of a specific mipmap level.
    // If level == 0, return the width of the base level (source image).
    // Width is always >= 1, to prevent non-square textures from having zero-sized levels.
    inline unsigned int width(unsigned int level = 0)
    {
        unsigned int w = m_width >> level;
        if (w > 0)
            return w;
        else
            return 1;
    }
    
    inline unsigned int height(unsigned int level = 0)
    {
        unsigned int h = m_height >> level;
        if (h > 0)
            return h;
        else
            return 1;
    }

protected:

    inline unsigned char* internalFetch(unsigned int s, unsigned int t, unsigned int level)
    {
        assert((s >= 0) && (s < width(level)));
        assert((t >= 0) && (t < height(level)));
        return m_levels[level] + 4 * ((width(level) * t) + s);
    }


private:

    // Fairly permanent variables   
    unsigned int m_width, m_height;
    Type m_type;
    TexObj m_texObj;
    bool m_mipmapped;
    
    // Pyramid levels (assumes 4 bytes per pixel for now)
    unsigned char **m_levels;
    unsigned int m_numLevels;   // Number of mipmaps + base texture

    // Cached variables (Depend on previous private variables)
    GLint       m_internalFormat;
    GLenum      m_format;
    GLenum      m_componentFormat;
};


#endif // MAYA_API_MTexture